21257515402 has 8 divisors (see below), whose sum is σ = 32119020036. Its totient is φ = 10551175392.

The previous prime is 21257515387. The next prime is 21257515403. The reversal of 21257515402 is 20451575212.

21257515402 is digitally balanced in base 5, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 20010648681 + 1246866721 = 141459^2 + 35311^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21257515402² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21257515403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38790813 + ... + 38791360.

Almost surely, 2^21257515402 is an apocalyptic number.

21257515402 is a deficient number, since it is larger than the sum of its proper divisors (10861504634).

21257515402 is a wasteful number, since it uses less digits than its factorization.

21257515402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77582312.

The product of its (nonzero) digits is 28000, while the sum is 34.

The spelling of 21257515402 in words is "twenty-one billion, two hundred fifty-seven million, five hundred fifteen thousand, four hundred two".