253 (two hundred [and] fifty-three) is the natural number following 252 and preceding 254.
In mathematics
253 is:
- a semiprime since it is the product of 2 primes.
- a 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.
is a prime number. Its decimal expansion is 252 nines, an eight, and 253 more nines.
References
- ^ Sloane, N. J. A. (ed.). "Sequence A000217 (triangular numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.