15997891 has 32 divisors (see below), whose sum is σ = 20901888. Its totient is φ = 11905920.

The previous prime is 15997889. The next prime is 15997957. The reversal of 15997891 is 19879951.

It is a happy number.

It is not a de Polignac number, because 15997891 - 2¹ = 15997889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15997841) 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 in 31 ways as a sum of consecutive naturals, for example, 149460 + ... + 149566.

It is an arithmetic number, because the mean of its divisors is an integer number (653184).

Almost surely, 2^15997891 is an apocalyptic number.

15997891 is a deficient number, since it is larger than the sum of its proper divisors (4903997).

15997891 is a wasteful number, since it uses less digits than its factorization.

15997891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211.

The product of its digits is 204120, while the sum is 49.

The square root of 15997891 is about 3999.7363663122. The cubic root of 15997891 is about 251.9731379363.

The spelling of 15997891 in words is "fifteen million, nine hundred ninety-seven thousand, eight hundred ninety-one".