15991649 has 2 divisors, whose sum is σ = 15991650. Its totient is φ = 15991648.

The previous prime is 15991639. The next prime is 15991663. The reversal of 15991649 is 94619951.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14961424 + 1030225 = 3868^2 + 1015^2 .

It is a cyclic number.

It is not a de Polignac number, because 15991649 - 2²⁰ = 14943073 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (15991639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7995824 + 7995825.

It is an arithmetic number, because the mean of its divisors is an integer number (7995825).

Almost surely, 2^15991649 is an apocalyptic number.

It is an amenable number.

15991649 is a deficient number, since it is larger than the sum of its proper divisors (1).

15991649 is an equidigital number, since it uses as much as digits as its factorization.

15991649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 87480, while the sum is 44.

The square root of 15991649 is about 3998.9559887551. The cubic root of 15991649 is about 251.9403623466.

The spelling of 15991649 in words is "fifteen million, nine hundred ninety-one thousand, six hundred forty-nine".