21125656 has 8 divisors (see below), whose sum is σ = 39610620. Its totient is φ = 10562824.

The previous prime is 21125651. The next prime is 21125669. The reversal of 21125656 is 65652112.

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 (28) 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 (21125651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1320346 + ... + 1320361.

Almost surely, 2^21125656 is an apocalyptic number.

It is an amenable number.

21125656 is a deficient number, since it is larger than the sum of its proper divisors (18484964).

21125656 is a wasteful number, since it uses less digits than its factorization.

21125656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2640713 (or 2640709 counting only the distinct ones).

The product of its digits is 3600, while the sum is 28.

The square root of 21125656 is about 4596.2654405506. The cubic root of 21125656 is about 276.4416020952.

Adding to 21125656 its reverse (65652112), we get a palindrome (86777768).

The spelling of 21125656 in words is "twenty-one million, one hundred twenty-five thousand, six hundred fifty-six".