21687193700 has 18 divisors (see below), whose sum is σ = 47061210546. Its totient is φ = 8674877440.

The previous prime is 21687193687. The next prime is 21687193711. The reversal of 21687193700 is 739178612.

It can be written as a sum of positive squares in 3 ways, for example, as 472105984 + 21215087716 = 21728^2 + 145654^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 108435869 + ... + 108436068.

It is an arithmetic number, because the mean of its divisors is an integer number (2614511697).

Almost surely, 2^21687193700 is an apocalyptic number.

21687193700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21687193700 is an abundant number, since it is smaller than the sum of its proper divisors (25374016846).

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

21687193700 is a wasteful number, since it uses less digits than its factorization.

21687193700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216871951 (or 216871944 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 44.

The spelling of 21687193700 in words is "twenty-one billion, six hundred eighty-seven million, one hundred ninety-three thousand, seven hundred".