253 (number)

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

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.