21407656 has 8 divisors (see below), whose sum is σ = 40139370. Its totient is φ = 10703824.

The previous prime is 21407653. The next prime is 21407663. The reversal of 21407656 is 65670412.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 14699556 + 6708100 = 3834^2 + 2590^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21407653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1337971 + ... + 1337986.

Almost surely, 2^21407656 is an apocalyptic number.

It is an amenable number.

21407656 is a deficient number, since it is larger than the sum of its proper divisors (18731714).

21407656 is a wasteful number, since it uses less digits than its factorization.

21407656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2675963 (or 2675959 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 21407656 is about 4626.8408228509. The cubic root of 21407656 is about 277.6662143041. Note that the first 3 decimals are identical.

The spelling of 21407656 in words is "twenty-one million, four hundred seven thousand, six hundred fifty-six".