21612566566646 has 16 divisors (see below), whose sum is σ = 36506857310208. Its totient is φ = 9506994090600.

The previous prime is 21612566566631. The next prime is 21612566566651. The reversal of 21612566566646 is 64666566521612.

It is a Harshad number since it is a multiple of its sum of digits (62).

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, 15844989470 + ... + 15844990833.

It is an arithmetic number, because the mean of its divisors is an integer number (2281678581888).

Almost surely, 2^{21612566566646} is an apocalyptic number.

21612566566646 is a deficient number, since it is larger than the sum of its proper divisors (14894290743562).

21612566566646 is a wasteful number, since it uses less digits than its factorization.

21612566566646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31689980347.

The product of its digits is 111974400, while the sum is 62.

The spelling of 21612566566646 in words is "twenty-one trillion, six hundred twelve billion, five hundred sixty-six million, five hundred sixty-six thousand, six hundred forty-six".