21615451566 has 32 divisors (see below), whose sum is σ = 45509748480. Its totient is φ = 6830888064.

The previous prime is 21615451553. The next prime is 21615451573. The reversal of 21615451566 is 66515451612.

It is a congruent number.

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, 677476 + ... + 708663.

It is an arithmetic number, because the mean of its divisors is an integer number (1422179640).

Almost surely, 2^21615451566 is an apocalyptic number.

21615451566 is an abundant number, since it is smaller than the sum of its proper divisors (23894296914).

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

21615451566 is a wasteful number, since it uses less digits than its factorization.

21615451566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1386280.

The product of its digits is 216000, while the sum is 42.

The spelling of 21615451566 in words is "twenty-one billion, six hundred fifteen million, four hundred fifty-one thousand, five hundred sixty-six".