21686870836 has 12 divisors (see below), whose sum is σ = 38343282628. Its totient is φ = 10731647232.

The previous prime is 21686870833. The next prime is 21686870851. The reversal of 21686870836 is 63807868612.

It can be written as a sum of positive squares in 2 ways, for example, as 14222947600 + 7463923236 = 119260^2 + 86394^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21686870831) 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, 27946611 + ... + 27947386.

Almost surely, 2^21686870836 is an apocalyptic number.

It is an amenable number.

21686870836 is a deficient number, since it is larger than the sum of its proper divisors (16656411792).

21686870836 is a wasteful number, since it uses less digits than its factorization.

21686870836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55894098 (or 55894096 counting only the distinct ones).

The product of its (nonzero) digits is 4644864, while the sum is 55.

The spelling of 21686870836 in words is "twenty-one billion, six hundred eighty-six million, eight hundred seventy thousand, eight hundred thirty-six".