15999997 has 4 divisors (see below), whose sum is σ = 17230780. Its totient is φ = 14769216.

The previous prime is 15999989. The next prime is 16000057. The reversal of 15999997 is 79999951.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1779556 + 14220441 = 1334^2 + 3771^2 .

It is a cyclic number.

It is not a de Polignac number, because 15999997 - 2³ = 15999989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15993997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 615372 + ... + 615397.

It is an arithmetic number, because the mean of its divisors is an integer number (4307695).

Almost surely, 2^15999997 is an apocalyptic number.

It is an amenable number.

15999997 is a deficient number, since it is larger than the sum of its proper divisors (1230783).

15999997 is a wasteful number, since it uses less digits than its factorization.

15999997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1230782.

The product of its digits is 2066715, while the sum is 58.

The square root of 15999997 is about 3999.9996250000. Note that the first 3 decimals coincide. The cubic root of 15999997 is about 251.9841942300.

The spelling of 15999997 in words is "fifteen million, nine hundred ninety-nine thousand, nine hundred ninety-seven".