21516902861 has 4 divisors (see below), whose sum is σ = 21789268800. Its totient is φ = 21244536924.

The previous prime is 21516902851. The next prime is 21516902863. The reversal of 21516902861 is 16820961512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21516902861 - 2¹⁰ = 21516901837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516902863) 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, 136182851 + ... + 136183008.

It is an arithmetic number, because the mean of its divisors is an integer number (5447317200).

Almost surely, 2^21516902861 is an apocalyptic number.

It is an amenable number.

21516902861 is a deficient number, since it is larger than the sum of its proper divisors (272365939).

21516902861 is an equidigital number, since it uses as much as digits as its factorization.

21516902861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 272365938.

The product of its (nonzero) digits is 51840, while the sum is 41.

The spelling of 21516902861 in words is "twenty-one billion, five hundred sixteen million, nine hundred two thousand, eight hundred sixty-one".