21691067904 has 180 divisors, whose sum is σ = 68812111368. Its totient is φ = 6572881920.

The previous prime is 21691067891. The next prime is 21691067933. The reversal of 21691067904 is 40976019612.

It is a self number, because there is not a number n which added to its sum of digits gives 21691067904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 538117 + ... + 577019.

Almost surely, 2^21691067904 is an apocalyptic number.

21691067904 is a gapful number since it is divisible by the number (24) 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 21691067904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34406055684).

21691067904 is an abundant number, since it is smaller than the sum of its proper divisors (47121043464).

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

21691067904 is a wasteful number, since it uses less digits than its factorization.

21691067904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38949 (or 38919 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The spelling of 21691067904 in words is "twenty-one billion, six hundred ninety-one million, sixty-seven thousand, nine hundred four".