21691605600 has 1440 divisors, whose sum is σ = 100045471680. Its totient is φ = 4459069440.

The previous prime is 21691605599. The next prime is 21691605619. The reversal of 21691605600 is 650619612.

21691605600 is a `hidden beast` number, since 2 + 1 + 6 + 91 + 6 + 0 + 560 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1440).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 223624752 + ... + 223624848.

It is an arithmetic number, because the mean of its divisors is an integer number (69476022).

Almost surely, 2^21691605600 is an apocalyptic number.

21691605600 is a gapful number since it is divisible by the number (20) 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 21691605600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50022735840).

21691605600 is an abundant number, since it is smaller than the sum of its proper divisors (78353866080).

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

21691605600 is a wasteful number, since it uses less digits than its factorization.

21691605600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182 (or 160 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The spelling of 21691605600 in words is "twenty-one billion, six hundred ninety-one million, six hundred five thousand, six hundred".