21315502251 has 24 divisors (see below), whose sum is σ = 31857930000. Its totient is φ = 13717230912.

The previous prime is 21315502237. The next prime is 21315502253. The reversal of 21315502251 is 15220551312.

21315502251 is a `hidden beast` number, since 2 + 131 + 5 + 502 + 25 + 1 = 666.

It is not a de Polignac number, because 21315502251 - 2¹⁰ = 21315501227 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21315502253) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1941325 + ... + 1952273.

It is an arithmetic number, because the mean of its divisors is an integer number (1327413750).

Almost surely, 2^21315502251 is an apocalyptic number.

21315502251 is a deficient number, since it is larger than the sum of its proper divisors (10542427749).

21315502251 is a wasteful number, since it uses less digits than its factorization.

21315502251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18443 (or 18440 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 27.

The spelling of 21315502251 in words is "twenty-one billion, three hundred fifteen million, five hundred two thousand, two hundred fifty-one".