21081737520 has 120 divisors (see below), whose sum is σ = 72526420512. Its totient is φ = 5484672000.

The previous prime is 21081737513. The next prime is 21081737563. The reversal of 21081737520 is 2573718012.

21081737520 is a `hidden beast` number, since 21 + 0 + 81 + 7 + 37 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 327556 + ... + 386595.

Almost surely, 2^21081737520 is an apocalyptic number.

21081737520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21081737520 is an abundant number, since it is smaller than the sum of its proper divisors (51444682992).

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

21081737520 is a wasteful number, since it uses less digits than its factorization.

21081737520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 714211 (or 714202 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The spelling of 21081737520 in words is "twenty-one billion, eighty-one million, seven hundred thirty-seven thousand, five hundred twenty".