2015991 has 6 divisors (see below), whose sum is σ = 2912000. Its totient is φ = 1343988.

The previous prime is 2015977. The next prime is 2015999. The reversal of 2015991 is 1995102.

It is a happy number.

It is not a de Polignac number, because 2015991 - 2⁷ = 2015863 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2015999) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 111991 + ... + 112008.

2^2015991 is an apocalyptic number.

2015991 is a deficient number, since it is larger than the sum of its proper divisors (896009).

2015991 is a wasteful number, since it uses less digits than its factorization.

2015991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224005 (or 224002 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 27.

The square root of 2015991 is about 1419.8559786119. The cubic root of 2015991 is about 126.3270039660.

The spelling of 2015991 in words is "two million, fifteen thousand, nine hundred ninety-one".