21002521261 has 16 divisors (see below), whose sum is σ = 21660661440. Its totient is φ = 20352608640.

The previous prime is 21002521237. The next prime is 21002521313. The reversal of 21002521261 is 16212520012.

It is a de Polignac number, because none of the positive numbers 2^k-21002521261 is a prime.

It is a super-2 number, since 2×21002521261² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002524261) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3873010 + ... + 3878428.

It is an arithmetic number, because the mean of its divisors is an integer number (1353791340).

Almost surely, 2^21002521261 is an apocalyptic number.

It is an amenable number.

21002521261 is a deficient number, since it is larger than the sum of its proper divisors (658140179).

21002521261 is a wasteful number, since it uses less digits than its factorization.

21002521261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6156.

The product of its (nonzero) digits is 480, while the sum is 22.

The spelling of 21002521261 in words is "twenty-one billion, two million, five hundred twenty-one thousand, two hundred sixty-one".