21159657 has 8 divisors (see below), whose sum is σ = 31347680. Its totient is φ = 14106420.

The previous prime is 21159653. The next prime is 21159683. The reversal of 21159657 is 75695112.

21159657 is a `hidden beast` number, since 2 + 11 + 596 + 57 = 666.

It is not a de Polignac number, because 21159657 - 2² = 21159653 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21159653) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 391819 + ... + 391872.

It is an arithmetic number, because the mean of its divisors is an integer number (3918460).

Almost surely, 2^21159657 is an apocalyptic number.

21159657 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21159657 is a deficient number, since it is larger than the sum of its proper divisors (10188023).

21159657 is an equidigital number, since it uses as much as digits as its factorization.

21159657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783700 (or 783694 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 21159657 is about 4599.9627172402. The cubic root of 21159657 is about 276.5898302781.

The spelling of 21159657 in words is "twenty-one million, one hundred fifty-nine thousand, six hundred fifty-seven".