15997591 has 4 divisors (see below), whose sum is σ = 16369672. Its totient is φ = 15625512.

The previous prime is 15997571. The next prime is 15997609. The reversal of 15997591 is 19579951.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19579951 = 3343 ⋅5857.

It is not a de Polignac number, because 15997591 - 2⁵ = 15997559 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 (15997571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 185976 + ... + 186061.

It is an arithmetic number, because the mean of its divisors is an integer number (4092418).

Almost surely, 2^15997591 is an apocalyptic number.

15997591 is a deficient number, since it is larger than the sum of its proper divisors (372081).

15997591 is an equidigital number, since it uses as much as digits as its factorization.

15997591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 372080.

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

The square root of 15997591 is about 3999.6988636646. The cubic root of 15997591 is about 251.9715628867.

The spelling of 15997591 in words is "fifteen million, nine hundred ninety-seven thousand, five hundred ninety-one".