21388456 has 8 divisors (see below), whose sum is σ = 40103370. Its totient is φ = 10694224.

The previous prime is 21388447. The next prime is 21388469. The reversal of 21388456 is 65488312.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 320356 = 4590^2 + 566^2 .

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

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1336771 + ... + 1336786.

Almost surely, 2^21388456 is an apocalyptic number.

It is an amenable number.

21388456 is a deficient number, since it is larger than the sum of its proper divisors (18714914).

21388456 is a wasteful number, since it uses less digits than its factorization.

21388456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2673563 (or 2673559 counting only the distinct ones).

The product of its digits is 46080, while the sum is 37.

The square root of 21388456 is about 4624.7655075690. The cubic root of 21388456 is about 277.5831788095.

The spelling of 21388456 in words is "twenty-one million, three hundred eighty-eight thousand, four hundred fifty-six".