21651665225664 has 56 divisors (see below), whose sum is σ = 57288077120848. Its totient is φ = 7217047941120.

The previous prime is 21651665225657. The next prime is 21651665225669. The reversal of 21651665225664 is 46652256615612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651665225669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6762024 + ... + 9435480.

It is an arithmetic number, because the mean of its divisors is an integer number (1023001377158).

Almost surely, 2^{21651665225664} is an apocalyptic number.

21651665225664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21651665225664 is an abundant number, since it is smaller than the sum of its proper divisors (35636411895184).

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

21651665225664 is a wasteful number, since it uses less digits than its factorization.

21651665225664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2715653 (or 2715643 counting only the distinct ones).

The product of its digits is 31104000, while the sum is 57.

The spelling of 21651665225664 in words is "twenty-one trillion, six hundred fifty-one billion, six hundred sixty-five million, two hundred twenty-five thousand, six hundred sixty-four".