21113957 has 2 divisors, whose sum is σ = 21113958. Its totient is φ = 21113956.

The previous prime is 21113941. The next prime is 21113971. The reversal of 21113957 is 75931112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20784481 + 329476 = 4559^2 + 574^2 .

It is a cyclic number.

It is not a de Polignac number, because 21113957 - 2⁴ = 21113941 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21113927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556978 + 10556979.

It is an arithmetic number, because the mean of its divisors is an integer number (10556979).

Almost surely, 2^21113957 is an apocalyptic number.

It is an amenable number.

21113957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21113957 is an equidigital number, since it uses as much as digits as its factorization.

21113957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1890, while the sum is 29.

The square root of 21113957 is about 4594.9926006469. The cubic root of 21113957 is about 276.3905632465.

The spelling of 21113957 in words is "twenty-one million, one hundred thirteen thousand, nine hundred fifty-seven".