15599981 has 2 divisors, whose sum is σ = 15599982. Its totient is φ = 15599980.

The previous prime is 15599959. The next prime is 15600001. The reversal of 15599981 is 18999551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10465225 + 5134756 = 3235^2 + 2266^2 .

It is an emirp because it is prime and its reverse (18999551) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15599981 - 2¹⁸ = 15337837 is a prime.

It is a super-2 number, since 2×15599981² = 486718814400722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15599281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7799990 + 7799991.

It is an arithmetic number, because the mean of its divisors is an integer number (7799991).

Almost surely, 2^15599981 is an apocalyptic number.

It is an amenable number.

15599981 is a deficient number, since it is larger than the sum of its proper divisors (1).

15599981 is an equidigital number, since it uses as much as digits as its factorization.

15599981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145800, while the sum is 47.

The square root of 15599981 is about 3949.6811263696. The cubic root of 15599981 is about 249.8664940507.

The spelling of 15599981 in words is "fifteen million, five hundred ninety-nine thousand, nine hundred eighty-one".