15613921 has 2 divisors, whose sum is σ = 15613922. Its totient is φ = 15613920.

The previous prime is 15613909. The next prime is 15613931. The reversal of 15613921 is 12931651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13242321 + 2371600 = 3639^2 + 1540^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15613921 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 15613921.

It is not a weakly prime, because it can be changed into another prime (15613901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7806960 + 7806961.

It is an arithmetic number, because the mean of its divisors is an integer number (7806961).

Almost surely, 2^15613921 is an apocalyptic number.

It is an amenable number.

15613921 is a deficient number, since it is larger than the sum of its proper divisors (1).

15613921 is an equidigital number, since it uses as much as digits as its factorization.

15613921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 28.

The square root of 15613921 is about 3951.4454317376. The cubic root of 15613921 is about 249.9408980289.

The spelling of 15613921 in words is "fifteen million, six hundred thirteen thousand, nine hundred twenty-one".