21330961566 has 16 divisors (see below), whose sum is σ = 42666578688. Its totient is φ = 7109544600.

The previous prime is 21330961549. The next prime is 21330961573. The reversal of 21330961566 is 66516903312.

It is a congruent number.

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, 132940 + ... + 245631.

It is an arithmetic number, because the mean of its divisors is an integer number (2666661168).

Almost surely, 2^21330961566 is an apocalyptic number.

21330961566 is an abundant number, since it is smaller than the sum of its proper divisors (21335617122).

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

21330961566 is a wasteful number, since it uses less digits than its factorization.

21330961566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 387967.

The product of its (nonzero) digits is 174960, while the sum is 42.

The spelling of 21330961566 in words is "twenty-one billion, three hundred thirty million, nine hundred sixty-one thousand, five hundred sixty-six".