21388656 has 20 divisors (see below), whose sum is σ = 55254152. Its totient is φ = 7129536.

The previous prime is 21388651. The next prime is 21388663. The reversal of 21388656 is 65688312.

It is a happy number.

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 222751 + ... + 222846.

Almost surely, 2^21388656 is an apocalyptic number.

It is an amenable number.

21388656 is an abundant number, since it is smaller than the sum of its proper divisors (33865496).

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

21388656 is a wasteful number, since it uses less digits than its factorization.

21388656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445608 (or 445602 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 21388656 is about 4624.7871302364. The cubic root of 21388656 is about 277.5840440186.

The spelling of 21388656 in words is "twenty-one million, three hundred eighty-eight thousand, six hundred fifty-six".