3991915 has 4 divisors (see below), whose sum is σ = 4790304. Its totient is φ = 3193528.

The previous prime is 3991891. The next prime is 3991943. The reversal of 3991915 is 5191993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5191993 = 89 ⋅58337.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3991915 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 399187 + ... + 399196.

It is an arithmetic number, because the mean of its divisors is an integer number (1197576).

Almost surely, 2^3991915 is an apocalyptic number.

3991915 is a deficient number, since it is larger than the sum of its proper divisors (798389).

3991915 is an equidigital number, since it uses as much as digits as its factorization.

3991915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 798388.

The product of its digits is 10935, while the sum is 37.

The square root of 3991915 is about 1997.9777276036. The cubic root of 3991915 is about 158.6330819116.

The spelling of 3991915 in words is "three million, nine hundred ninety-one thousand, nine hundred fifteen".