21456408656 has 10 divisors (see below), whose sum is σ = 41571791802. Its totient is φ = 10728204320.

The previous prime is 21456408653. The next prime is 21456408671. The reversal of 21456408656 is 65680465412.

It can be written as a sum of positive squares in only one way, i.e., 14448040000 + 7008368656 = 120200^2 + 83716^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21456408656.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456408653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 670512755 + ... + 670512786.

Almost surely, 2^21456408656 is an apocalyptic number.

It is an amenable number.

21456408656 is a deficient number, since it is larger than the sum of its proper divisors (20115383146).

21456408656 is a wasteful number, since it uses less digits than its factorization.

21456408656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1341025549 (or 1341025543 counting only the distinct ones).

The product of its (nonzero) digits is 1382400, while the sum is 47.

The spelling of 21456408656 in words is "twenty-one billion, four hundred fifty-six million, four hundred eight thousand, six hundred fifty-six".