21671956656 has 360 divisors, whose sum is σ = 73796895744. Its totient is φ = 5806805760.

The previous prime is 21671956633. The next prime is 21671956661. The reversal of 21671956656 is 65665917612.

21671956656 is a `hidden beast` number, since 2 + 1 + 6 + 71 + 9 + 566 + 5 + 6 = 666.

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, 170645265 + ... + 170645391.

Almost surely, 2^21671956656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21671956656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36898447872).

21671956656 is an abundant number, since it is smaller than the sum of its proper divisors (52124939088).

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

21671956656 is a wasteful number, since it uses less digits than its factorization.

21671956656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349 (or 213 counting only the distinct ones).

The product of its digits is 4082400, while the sum is 54.

The spelling of 21671956656 in words is "twenty-one billion, six hundred seventy-one million, nine hundred fifty-six thousand, six hundred fifty-six".