21685640508 has 54 divisors (see below), whose sum is σ = 63766114776. Its totient is φ = 6195896784.

The previous prime is 21685640489. The next prime is 21685640513. The reversal of 21685640508 is 80504658612.

21685640508 is a `hidden beast` number, since 2 + 1 + 6 + 85 + 64 + 0 + 508 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 6144960 + ... + 6148487.

Almost surely, 2^21685640508 is an apocalyptic number.

21685640508 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21685640508 is an abundant number, since it is smaller than the sum of its proper divisors (42080474268).

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

21685640508 is a wasteful number, since it uses less digits than its factorization.

21685640508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12293471 (or 12293459 counting only the distinct ones).

The product of its (nonzero) digits is 460800, while the sum is 45.

The spelling of 21685640508 in words is "twenty-one billion, six hundred eighty-five million, six hundred forty thousand, five hundred eight".