15121991 has 2 divisors, whose sum is σ = 15121992. Its totient is φ = 15121990.

The previous prime is 15121987. The next prime is 15122033. The reversal of 15121991 is 19912151.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 15121991 - 2² = 15121987 is a prime.

It is a super-2 number, since 2×15121991² = 457349223608162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15121091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7560995 + 7560996.

It is an arithmetic number, because the mean of its divisors is an integer number (7560996).

Almost surely, 2^15121991 is an apocalyptic number.

15121991 is a deficient number, since it is larger than the sum of its proper divisors (1).

15121991 is an equidigital number, since it uses as much as digits as its factorization.

15121991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 810, while the sum is 29.

The square root of 15121991 is about 3888.7004255921. The cubic root of 15121991 is about 247.2879713204.

The spelling of 15121991 in words is "fifteen million, one hundred twenty-one thousand, nine hundred ninety-one".