21688638624 has 768 divisors, whose sum is σ = 76640256000. Its totient is φ = 5912248320.

The previous prime is 21688638619. The next prime is 21688638677. The reversal of 21688638624 is 42683688612.

21688638624 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 8 + 6 + 3 + 8 + 624 = 666.

It is a super-2 number, since 2×21688638624² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 198978282 + ... + 198978390.

It is an arithmetic number, because the mean of its divisors is an integer number (99792000).

Almost surely, 2^21688638624 is an apocalyptic number.

21688638624 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 21688638624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38320128000).

21688638624 is an abundant number, since it is smaller than the sum of its proper divisors (54951617376).

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

21688638624 is a wasteful number, since it uses less digits than its factorization.

21688638624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218 (or 204 counting only the distinct ones).

The product of its digits is 5308416, while the sum is 54.

The spelling of 21688638624 in words is "twenty-one billion, six hundred eighty-eight million, six hundred thirty-eight thousand, six hundred twenty-four".