3991591 has 4 divisors (see below), whose sum is σ = 4120384. Its totient is φ = 3862800.

The previous prime is 3991579. The next prime is 3991601. The reversal of 3991591 is 1951993.

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

It is a cyclic number.

It is not a de Polignac number, because 3991591 - 2²¹ = 1894439 is a prime.

It is a super-2 number, since 2×3991591² = 31865597422562, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 3991591.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991511) 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, 64350 + ... + 64411.

It is an arithmetic number, because the mean of its divisors is an integer number (1030096).

Almost surely, 2^3991591 is an apocalyptic number.

3991591 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

3991591 is a deficient number, since it is larger than the sum of its proper divisors (128793).

3991591 is a wasteful number, since it uses less digits than its factorization.

3991591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128792.

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

The square root of 3991591 is about 1997.8966439734. The cubic root of 3991591 is about 158.6287900275.

The spelling of 3991591 in words is "three million, nine hundred ninety-one thousand, five hundred ninety-one".