15559991 has 2 divisors, whose sum is σ = 15559992. Its totient is φ = 15559990.

The previous prime is 15559967. The next prime is 15560057. The reversal of 15559991 is 19995551.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (19995551) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15559991 - 2¹⁸ = 15297847 is a prime.

It is a super-2 number, since 2×15559991² = 484226639840162, which contains 22 as substring.

It is a Sophie Germain 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 (15559931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7779995 + 7779996.

It is an arithmetic number, because the mean of its divisors is an integer number (7779996).

Almost surely, 2^15559991 is an apocalyptic number.

15559991 is a deficient number, since it is larger than the sum of its proper divisors (1).

15559991 is an equidigital number, since it uses as much as digits as its factorization.

15559991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 91125, while the sum is 44.

The square root of 15559991 is about 3944.6154438678. The cubic root of 15559991 is about 249.6528033746.

The spelling of 15559991 in words is "fifteen million, five hundred fifty-nine thousand, nine hundred ninety-one".