21678007656 has 128 divisors (see below), whose sum is σ = 57233848320. Its totient is φ = 6828966144.

The previous prime is 21678007609. The next prime is 21678007667. The reversal of 21678007656 is 65670087612.

It is a super-2 number, since 2×21678007656² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17724661 + ... + 17725883.

It is an arithmetic number, because the mean of its divisors is an integer number (447139440).

Almost surely, 2^21678007656 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 21678007656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28616924160).

21678007656 is an abundant number, since it is smaller than the sum of its proper divisors (35555840664).

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

21678007656 is a wasteful number, since it uses less digits than its factorization.

21678007656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1615 (or 1611 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 48.

The spelling of 21678007656 in words is "twenty-one billion, six hundred seventy-eight million, seven thousand, six hundred fifty-six".