21156533816 has 32 divisors (see below), whose sum is σ = 43281097200. Its totient is φ = 9615191040.

The previous prime is 21156533809. The next prime is 21156533851. The reversal of 21156533816 is 61833565112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 794120 + ... + 820328.

Almost surely, 2^21156533816 is an apocalyptic number.

It is an amenable number.

21156533816 is an abundant number, since it is smaller than the sum of its proper divisors (22124563384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21156533816 is a wasteful number, since it uses less digits than its factorization.

21156533816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35399 (or 35395 counting only the distinct ones).

The product of its digits is 129600, while the sum is 41.

The spelling of 21156533816 in words is "twenty-one billion, one hundred fifty-six million, five hundred thirty-three thousand, eight hundred sixteen".