21668663657652 has 96 divisors (see below), whose sum is σ = 55698201968640. Its totient is φ = 6501862120320.

The previous prime is 21668663657647. The next prime is 21668663657653. The reversal of 21668663657652 is 25675636686612.

It is a happy number.

It is a Smith number, since the sum of its digits (69) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668663657653) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22065453 + ... + 23026539.

It is an arithmetic number, because the mean of its divisors is an integer number (580189603840).

Almost surely, 2^{21668663657652} is an apocalyptic number.

21668663657652 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21668663657652, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27849100984320).

21668663657652 is an abundant number, since it is smaller than the sum of its proper divisors (34029538310988).

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

21668663657652 is a wasteful number, since it uses less digits than its factorization.

21668663657652 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 962781 (or 962779 counting only the distinct ones).

The product of its digits is 783820800, while the sum is 69.

The spelling of 21668663657652 in words is "twenty-one trillion, six hundred sixty-eight billion, six hundred sixty-three million, six hundred fifty-seven thousand, six hundred fifty-two".