15091991 has 2 divisors, whose sum is σ = 15091992. Its totient is φ = 15091990.

The previous prime is 15091943. The next prime is 15092003. The reversal of 15091991 is 19919051.

15091991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is an emirp because it is prime and its reverse (19919051) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15091991 - 2²² = 10897687 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15091931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7545995 + 7545996.

It is an arithmetic number, because the mean of its divisors is an integer number (7545996).

Almost surely, 2^15091991 is an apocalyptic number.

15091991 is a deficient number, since it is larger than the sum of its proper divisors (1).

15091991 is an equidigital number, since it uses as much as digits as its factorization.

15091991 is an evil number, because the sum of its binary digits is even.

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

The square root of 15091991 is about 3884.8411807949. The cubic root of 15091991 is about 247.1243343492.

The spelling of 15091991 in words is "fifteen million, ninety-one thousand, nine hundred ninety-one".