20891597 has 2 divisors, whose sum is σ = 20891598. Its totient is φ = 20891596.

The previous prime is 20891587. The next prime is 20891603. The reversal of 20891597 is 79519802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14485636 + 6405961 = 3806^2 + 2531^2 .

It is a cyclic number.

It is not a de Polignac number, because 20891597 - 2⁴ = 20891581 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20891557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10445798 + 10445799.

It is an arithmetic number, because the mean of its divisors is an integer number (10445799).

Almost surely, 2^20891597 is an apocalyptic number.

It is an amenable number.

20891597 is a deficient number, since it is larger than the sum of its proper divisors (1).

20891597 is an equidigital number, since it uses as much as digits as its factorization.

20891597 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 20891597 is about 4570.7326546190. The cubic root of 20891597 is about 275.4168751736.

The spelling of 20891597 in words is "twenty million, eight hundred ninety-one thousand, five hundred ninety-seven".