15977921 has 2 divisors, whose sum is σ = 15977922. Its totient is φ = 15977920.

The previous prime is 15977887. The next prime is 15977933. The reversal of 15977921 is 12977951.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15054400 + 923521 = 3880^2 + 961^2 .

It is a cyclic number.

It is not a de Polignac number, because 15977921 - 2²² = 11783617 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (15977971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7988960 + 7988961.

It is an arithmetic number, because the mean of its divisors is an integer number (7988961).

Almost surely, 2^15977921 is an apocalyptic number.

It is an amenable number.

15977921 is a deficient number, since it is larger than the sum of its proper divisors (1).

15977921 is an equidigital number, since it uses as much as digits as its factorization.

15977921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 39690, while the sum is 41.

The square root of 15977921 is about 3997.2391722288. The cubic root of 15977921 is about 251.8682491361.

The spelling of 15977921 in words is "fifteen million, nine hundred seventy-seven thousand, nine hundred twenty-one".