21044635668 has 216 divisors, whose sum is σ = 63611708160. Its totient is φ = 5745841920.

The previous prime is 21044635621. The next prime is 21044635673. The reversal of 21044635668 is 86653644012.

21044635668 is a `hidden beast` number, since 2 + 1 + 0 + 4 + 4 + 635 + 6 + 6 + 8 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 23100133 + ... + 23101043.

Almost surely, 2^21044635668 is an apocalyptic number.

21044635668 is a gapful number since it is divisible by the number (28) 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 21044635668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31805854080).

21044635668 is an abundant number, since it is smaller than the sum of its proper divisors (42567072492).

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

21044635668 is a wasteful number, since it uses less digits than its factorization.

21044635668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1095 (or 1061 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 45.

The spelling of 21044635668 in words is "twenty-one billion, forty-four million, six hundred thirty-five thousand, six hundred sixty-eight".