21515855280 has 80 divisors (see below), whose sum is σ = 66936724704. Its totient is φ = 5717125120.

The previous prime is 21515855243. The next prime is 21515855327. The reversal of 21515855280 is 8255851512.

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, 92079 + ... + 226958.

Almost surely, 2^21515855280 is an apocalyptic number.

21515855280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21515855280 is an abundant number, since it is smaller than the sum of its proper divisors (45420869424).

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

21515855280 is a wasteful number, since it uses less digits than its factorization.

21515855280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319334 (or 319328 counting only the distinct ones).

The product of its (nonzero) digits is 160000, while the sum is 42.

The spelling of 21515855280 in words is "twenty-one billion, five hundred fifteen million, eight hundred fifty-five thousand, two hundred eighty".