15991091 has 4 divisors (see below), whose sum is σ = 16229832. Its totient is φ = 15752352.

The previous prime is 15991037. The next prime is 15991097. The reversal of 15991091 is 19019951.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19019951 = 53 ⋅358867.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15991091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15991097) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 119270 + ... + 119403.

It is an arithmetic number, because the mean of its divisors is an integer number (4057458).

Almost surely, 2^15991091 is an apocalyptic number.

15991091 is a deficient number, since it is larger than the sum of its proper divisors (238741).

15991091 is an equidigital number, since it uses as much as digits as its factorization.

15991091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238740.

The product of its (nonzero) digits is 3645, while the sum is 35.

The square root of 15991091 is about 3998.8862199367. The cubic root of 15991091 is about 251.9374319764.

The spelling of 15991091 in words is "fifteen million, nine hundred ninety-one thousand, ninety-one".