15897991 has 8 divisors (see below), whose sum is σ = 16629984. Its totient is φ = 15169440.

The previous prime is 15897983. The next prime is 15898007. The reversal of 15897991 is 19979851.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 15897991 - 2³ = 15897983 is a prime.

It is a super-2 number, since 2×15897991² = 505492235672162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15897391) 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 7 ways as a sum of consecutive naturals, for example, 15061 + ... + 16081.

It is an arithmetic number, because the mean of its divisors is an integer number (2078748).

Almost surely, 2^15897991 is an apocalyptic number.

15897991 is a deficient number, since it is larger than the sum of its proper divisors (731993).

15897991 is a wasteful number, since it uses less digits than its factorization.

15897991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1721.

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

The square root of 15897991 is about 3987.2284860539. The cubic root of 15897991 is about 251.4475541705.

The spelling of 15897991 in words is "fifteen million, eight hundred ninety-seven thousand, nine hundred ninety-one".