21157072 has 10 divisors (see below), whose sum is σ = 40991858. Its totient is φ = 10578528.

The previous prime is 21157067. The next prime is 21157091. The reversal of 21157072 is 27075112.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21123216 + 33856 = 4596^2 + 184^2 .

It is a super-2 number, since 2×21157072² = 895243391226368, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 661143 + ... + 661174.

Almost surely, 2^21157072 is an apocalyptic number.

It is an amenable number.

21157072 is a deficient number, since it is larger than the sum of its proper divisors (19834786).

21157072 is a wasteful number, since it uses less digits than its factorization.

21157072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1322325 (or 1322319 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21157072 is about 4599.6817281199. The cubic root of 21157072 is about 276.5785664876.

The spelling of 21157072 in words is "twenty-one million, one hundred fifty-seven thousand, seventy-two".