21308913928 has 32 divisors (see below), whose sum is σ = 40938975000. Its totient is φ = 10391984640.

The previous prime is 21308913919. The next prime is 21308913943. The reversal of 21308913928 is 82931980312.

It can be written as a sum of positive squares in 4 ways, for example, as 19926710244 + 1382203684 = 141162^2 + 37178^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2274598 + ... + 2283946.

Almost surely, 2^21308913928 is an apocalyptic number.

It is an amenable number.

21308913928 is a deficient number, since it is larger than the sum of its proper divisors (19630061072).

21308913928 is a wasteful number, since it uses less digits than its factorization.

21308913928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16345 (or 16341 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 46.

The spelling of 21308913928 in words is "twenty-one billion, three hundred eight million, nine hundred thirteen thousand, nine hundred twenty-eight".