21705016520 has 32 divisors (see below), whose sum is σ = 53275950720. Its totient is φ = 7892733120.

The previous prime is 21705016517. The next prime is 21705016537. The reversal of 21705016520 is 2561050712.

It is a super-2 number, since 2×21705016520² (a number of 21 digits) contains 22 as substring.

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, 24664352 + ... + 24665231.

It is an arithmetic number, because the mean of its divisors is an integer number (1664873460).

Almost surely, 2^21705016520 is an apocalyptic number.

21705016520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21705016520 is an abundant number, since it is smaller than the sum of its proper divisors (31570934200).

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

21705016520 is a wasteful number, since it uses less digits than its factorization.

21705016520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49329605 (or 49329601 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 29.

The spelling of 21705016520 in words is "twenty-one billion, seven hundred five million, sixteen thousand, five hundred twenty".