15997 has 4 divisors (see below), whose sum is σ = 16956. Its totient is φ = 15040.

The previous prime is 15991. The next prime is 16001. The reversal of 15997 is 79951.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79951 = 17 ⋅4703.

It can be written as a sum of positive squares in 2 ways, for example, as 11236 + 4761 = 106^2 + 69^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15997 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 7 and base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 454 + ... + 487.

It is an arithmetic number, because the mean of its divisors is an integer number (4239).

15997 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

15997 is a deficient number, since it is larger than the sum of its proper divisors (959).

15997 is an equidigital number, since it uses as much as digits as its factorization.

15997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 958.

The product of its digits is 2835, while the sum is 31.

The square root of 15997 is about 126.4792473096. The cubic root of 15997 is about 25.1968459981.

It can be divided in two parts, 159 and 97, that added together give a 8-th power (256 = 2⁸).

The spelling of 15997 in words is "fifteen thousand, nine hundred ninety-seven".