253 (number)

253 (two hundred [and] fifty-three) is the natural number following 252 and preceding 254.

← 252 253 254 →
← 250 251 252 253 254 255 256 257 258 259 → List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	two hundred fifty-three
Ordinal	253rd (two hundred fifty-third)
Factorization	11 × 23
Divisors	1, 11, 23, 253
Greek numeral	ΣΝΓ´
Roman numeral	CCLIII
Binary	111111012
Ternary	1001013
Senary	11016
Octal	3758
Duodecimal	19112
Hexadecimal	FD16

In mathematics

253 is:

• a semiprime since it is the product of 2 primes.
• the 22nd triangular number.^[1]
• a star number.^[2]
• a centered heptagonal number.^[3]
• a centered nonagonal number.^[4]
• a Blum integer.^[5]
• a member of the 13-aliquot tree.

${\displaystyle 10^{506}-10^{253}-1}$ is a prime number. Its decimal expansion is 252 nines, an eight, and 253 more nines.

References

1. Sloane, N. J. A. (ed.). "Sequence A000217 (triangular numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
2. Sloane, N. J. A. (ed.). "Sequence A003154 (Centered 12-gonal numbers. Also star numbers: 6*n*(n-1) + 1)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
3. Sloane, N. J. A. (ed.). "Sequence A069099 (Centered heptagonal numbers. a(n) = (7*n^2 - 7*n + 2)/2)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
4. Sloane, N. J. A. (ed.). "Sequence A060544 (Centered 9-gonal numbers. (3n-1)*(3n-2)/2)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
5. Sloane, N. J. A. (ed.). "Sequence A016105 (Blum integers: numbers of the form p * q where p and q are distinct primes congruent to 3 (mod 4))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.