15718991 has 2 divisors, whose sum is σ = 15718992. Its totient is φ = 15718990.

The previous prime is 15718987. The next prime is 15718993. The reversal of 15718991 is 19981751.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 15718991 - 2² = 15718987 is a prime.

Together with 15718993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15718993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7859495 + 7859496.

It is an arithmetic number, because the mean of its divisors is an integer number (7859496).

Almost surely, 2^15718991 is an apocalyptic number.

15718991 is a deficient number, since it is larger than the sum of its proper divisors (1).

15718991 is an equidigital number, since it uses as much as digits as its factorization.

15718991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 41.

The square root of 15718991 is about 3964.7182749850. The cubic root of 15718991 is about 250.5002835311.

The spelling of 15718991 in words is "fifteen million, seven hundred eighteen thousand, nine hundred ninety-one".