21515630640 has 80 divisors (see below), whose sum is σ = 76226811648. Its totient is φ = 4917858048.

The previous prime is 21515630519. The next prime is 21515630659. The reversal of 21515630640 is 4603651512.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6401782 + ... + 6405141.

Almost surely, 2^21515630640 is an apocalyptic number.

21515630640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21515630640 is an abundant number, since it is smaller than the sum of its proper divisors (54711181008).

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

21515630640 is a wasteful number, since it uses less digits than its factorization.

21515630640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12806946 (or 12806940 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 33.

The spelling of 21515630640 in words is "twenty-one billion, five hundred fifteen million, six hundred thirty thousand, six hundred forty".