21665624120666 has 32 divisors (see below), whose sum is σ = 32627863352448. Its totient is φ = 10789741670400.

The previous prime is 21665624120633. The next prime is 21665624120743. The reversal of 21665624120666 is 66602142656612.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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, 4048889891 + ... + 4048895241.

It is an arithmetic number, because the mean of its divisors is an integer number (1019620729764).

Almost surely, 2^{21665624120666} is an apocalyptic number.

21665624120666 is a deficient number, since it is larger than the sum of its proper divisors (10962239231782).

21665624120666 is a wasteful number, since it uses less digits than its factorization.

21665624120666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10646.

The product of its (nonzero) digits is 7464960, while the sum is 53.

The spelling of 21665624120666 in words is "twenty-one trillion, six hundred sixty-five billion, six hundred twenty-four million, one hundred twenty thousand, six hundred sixty-six".