21651205165660 has 96 divisors (see below), whose sum is σ = 53751234055680. Its totient is φ = 7170679726848.

The previous prime is 21651205165657. The next prime is 21651205165673. The reversal of 21651205165660 is 6656150215612.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21651205165660.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 14315122 + ... + 15755161.

It is an arithmetic number, because the mean of its divisors is an integer number (559908688080).

Almost surely, 2^{21651205165660} is an apocalyptic number.

21651205165660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21651205165660 is an abundant number, since it is smaller than the sum of its proper divisors (32100028890020).

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

21651205165660 is a wasteful number, since it uses less digits than its factorization.

21651205165660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30070475 (or 30070473 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 46.

The spelling of 21651205165660 in words is "twenty-one trillion, six hundred fifty-one billion, two hundred five million, one hundred sixty-five thousand, six hundred sixty".