Number

121

121 is a composite number, odd, a calendar year.

121 (one hundred twenty-one) is an odd 3-digit number. It is a composite number with 3 divisors, and factors as 11². It is a perfect square (11²). Its digits read the same forwards and backwards, so it is a palindromic number. Written other ways, in Roman numerals it is CXXI and in binary, 1111001.

Consecutive Digits Cube-Free Deficient Number Gapful Number Lazy Caterer Number Odious Number Palindrome Perfect Square Pernicious Number Powerful Number Recamán's Sequence Self Number Semiprime Smith Number Star Number Undulating Number Year

Interestingness

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13 notable facts · grade A

109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133

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Historical context — 121 AD

Calendar year

Year 121 (CXXI) was a common year starting on Tuesday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 121 BC

Calendar year

Year 121 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Year facts

Year type: Common year
Standard 365-day year; not divisible by 4 (or divisible by 100 but not 400).
Days in year: 365
ISO weeks: 52
Started on: Wednesday
January 1, 121
Ended on: Wednesday
December 31, 121
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 120s
120–129
Century: 2nd century
101–200
Millennium: 1st millennium
1–1000
Years ago: 1,905
1905 years before 2026.

In other calendars

Hebrew: 3881 / 3882 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Metal zodiac:Rooster
Sexagenary cycle position 58 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 664 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 113 / 114 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 43 / 42 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 4
Digit product: 2
Digital root: 4
Palindrome: Yes
Bit width: 7 bits
Recamán's sequence: a(158) = 121
Square (n²): 14,641
Cube (n³): 1,771,561
Square root (√n): 11
Divisor count: 3
σ(n) — sum of divisors: 133
φ(n) — Euler's totient: 110
Sum of prime factors: 22

Primality

Prime factorization: 11 ²

Nearest primes: 113 (−8) · 127 (+6)

Divisors & multiples

All divisors (3)

1 · 11 · 121

Aliquot sum (sum of proper divisors): 12

Factor pairs (a × b = 121)

1 × 121

11 × 11

First multiples

121 · 242 (double) · 363 · 484 · 605 · 726 · 847 · 968 · 1,089 · 1,210

Sums & aliquot sequence

As a sum of two squares: 0² + 11²

As consecutive integers: 60 + 61 6 + 7 + … + 16

Aliquot sequence: 121 → 12 → 16 → 15 → 9 → 4 → 3 → 1 → 0 — terminates at zero

Representations

In words: one hundred twenty-one
Ordinal: 121st
Roman numeral: CXXI
Binary: 1111001
Octal: 171
Hexadecimal: 0x79
Base64: eQ==
One's complement: 134 (8-bit)
Scientific notation: 1.21 × 10²
As a duration: 121 s = 2 minutes, 1 second

In other bases

ternary (3) 11111

quaternary (4) 1321

quinary (5) 441

senary (6) 321

septenary (7) 232

nonary (9) 144

undecimal (11) 100

duodecimal (12) a1

tridecimal (13) 94

tetradecimal (14) 89

pentadecimal (15) 81

Palindromic in base 3, base 7, base 8

As an angle

121°

121° ≈ 2.112 rad

Compass bearing: ESE (east-southeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹 𒁹
Egyptian hieroglyphic: 𓍢𓎆𓎆𓏺
Greek (Milesian): ρκαʹ
Mayan (base 20): 𝋦·𝋡
Chinese: 一百二十一
Chinese (financial): 壹佰貳拾壹

In other modern scripts

Eastern Arabic ١٢١ Devanagari १२१ Bengali ১২১ Tamil ௧௨௧ Thai ๑๒๑ Tibetan ༡༢༡ Khmer ១២១ Lao ໑໒໑ Burmese ၁၂၁

Digit at this position in famous constants

π — Pi (π): Digit 121 = 7
e — Euler's number (e): Digit 121 = 1
φ — Golden ratio (φ): Digit 121 = 2
√2 — Pythagoras's (√2): Digit 121 = 4
ln 2 — Natural log of 2: Digit 121 = 3
γ — Euler-Mascheroni (γ): Digit 121 = 0

Also seen as

ASCII character

As an ASCII codepoint, 121 is y. Printable ASCII character y.

Hex color

#000079

RGB(0, 0, 121)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.121.

Address: 0.0.0.121
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.121

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 121 Hz is closest to:

Concert pitch (A4 = 440 Hz): B2 (123.5 Hz, -35¢)
Scientific pitch (C4 = 256 Hz): B2 (120.8 Hz, +3¢)
Baroque pitch (A4 = 415 Hz): C3 (123.4 Hz, -34¢)

As a MIDI note number, 121 is C♯9 (8869.8 Hz at concert pitch).