21157597 has 2 divisors, whose sum is σ = 21157598. Its totient is φ = 21157596.

The previous prime is 21157573. The next prime is 21157601. The reversal of 21157597 is 79575112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10621081 + 10536516 = 3259^2 + 3246^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21157597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21157897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578798 + 10578799.

It is an arithmetic number, because the mean of its divisors is an integer number (10578799).

Almost surely, 2^21157597 is an apocalyptic number.

It is an amenable number.

21157597 is a deficient number, since it is larger than the sum of its proper divisors (1).

21157597 is an equidigital number, since it uses as much as digits as its factorization.

21157597 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22050, while the sum is 37.

The square root of 21157597 is about 4599.7387969318. The cubic root of 21157597 is about 276.5808541789.

The spelling of 21157597 in words is "twenty-one million, one hundred fifty-seven thousand, five hundred ninety-seven".