21239779656 has 32 divisors (see below), whose sum is σ = 53487044640. Its totient is φ = 7028247168.

The previous prime is 21239779633. The next prime is 21239779661. The reversal of 21239779656 is 65697793212.

It is a super-2 number, since 2×21239779656² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21239779596 and 21239779605.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3226606 + ... + 3233181.

It is an arithmetic number, because the mean of its divisors is an integer number (1671470145).

Almost surely, 2^21239779656 is an apocalyptic number.

It is an amenable number.

21239779656 is an abundant number, since it is smaller than the sum of its proper divisors (32247264984).

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

21239779656 is a wasteful number, since it uses less digits than its factorization.

21239779656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6459933 (or 6459929 counting only the distinct ones).

The product of its digits is 8573040, while the sum is 57.

The spelling of 21239779656 in words is "twenty-one billion, two hundred thirty-nine million, seven hundred seventy-nine thousand, six hundred fifty-six".