21731888720 has 20 divisors (see below), whose sum is σ = 50526641460. Its totient is φ = 8692755456.

The previous prime is 21731888713. The next prime is 21731888741. The reversal of 21731888720 is 2788813712.

It can be written as a sum of positive squares in 2 ways, for example, as 12292600384 + 9439288336 = 110872^2 + 97156^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135824225 + ... + 135824384.

It is an arithmetic number, because the mean of its divisors is an integer number (2526332073).

Almost surely, 2^21731888720 is an apocalyptic number.

21731888720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21731888720 is an abundant number, since it is smaller than the sum of its proper divisors (28794752740).

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

21731888720 is a wasteful number, since it uses less digits than its factorization.

21731888720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271648622 (or 271648616 counting only the distinct ones).

The product of its (nonzero) digits is 301056, while the sum is 47.

The spelling of 21731888720 in words is "twenty-one billion, seven hundred thirty-one million, eight hundred eighty-eight thousand, seven hundred twenty".