15597991 has 6 divisors (see below), whose sum is σ = 16118376. Its totient is φ = 15093900.

The previous prime is 15597977. The next prime is 15598003. The reversal of 15597991 is 19979551.

15597991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 15597991 - 2²³ = 7209383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15597961) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 7155 + ... + 9076.

It is an arithmetic number, because the mean of its divisors is an integer number (2686396).

Almost surely, 2^15597991 is an apocalyptic number.

15597991 is a deficient number, since it is larger than the sum of its proper divisors (520385).

15597991 is an equidigital number, since it uses as much as digits as its factorization.

15597991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16293 (or 16262 counting only the distinct ones).

The product of its digits is 127575, while the sum is 46.

The square root of 15597991 is about 3949.4291992641. The cubic root of 15597991 is about 249.8558689209.

The spelling of 15597991 in words is "fifteen million, five hundred ninety-seven thousand, nine hundred ninety-one".