Number analysis
100
100 is a composite even number that factors as 2^2 × 5^2.
100 is a composite even number that factors as 2^2 × 5^2.
The number itself
- Value
- 100
- Digits
- 3
- Digit sum
- 1
- Reversed
- 1
- Palindrome
- No
1 + 0 + 0
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 1.
Parity and primality
- Parity
- Even
- Prime
- No
- Prime factorisation
- 2^2 × 5^2
- Squarefree
- No
- Powerful
- Yes
- Möbius μ(n)
- 0
- Nearest primes
- 97 ← → 101
Divisible by 2.
Composite — it factors as 2^2 × 5^2.
2 distinct prime factors, 4 with multiplicity.
At least one prime appears squared.
Every prime factor appears at least squared.
Zero, because a squared prime divides n.
A gap of 4 between them.
Divisors
- Aliquot sum
- 117
- Classification
- Abundant
1, 2, 4, 5, 10, 20, 25, 50, 100
The proper divisors — everything except n itself.
Its proper divisors overshoot by 17.
How many integers from 1 to n share no factor with n.
Sums and additive structure
- Sum of two squares
- Yes
- Sum of three squares
- Yes
- Sum of four squares
- Yes
- Goldbach pair
- 3 + 97
0² + 10² = 100 · 6² + 8² = 100
Legendre's three-square theorem allows it.
Lagrange's four-square theorem: every non-negative integer is, without exception.
The smallest pair of primes summing to n. Goldbach’s conjecture says one always exists; it remains unproven.
Shapes and sequences
- Square number
- Yes — the 10th
Digit curiosities
- Happy number
- Yes
- Harshad number
- Yes
- Collatz trajectory
- 25 steps to 1
Repeatedly summing the squares of its digits reaches 1.
Divisible by its digit sum 1 — 100 ÷ 1 = 100.
Peaks at 100 along the way.
Written other ways
- Binary
- 1100100
- Octal
- 144
- Hexadecimal
- 64
- Base 36
- 2S
- In words
- one hundred
- Scientific notation
- 1.00 × 10^2
Is 100 a prime number?
Composite — it factors as 2^2 × 5^2.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 100 their own way.
- Greek (alphabetic)
- Ρʹ
- Tamil
- ௱
References
Further reading: Wikipedia · MathWorld · Wikidata
Notations, naming and the links above come from Wikidata, whose structured data is dedicated to the public domain under CC0-1.0. Retrieved 2026-10-07.