3991731 has 4 divisors (see below), whose sum is σ = 5322312. Its totient is φ = 2661152.

The previous prime is 3991727. The next prime is 3991747. The reversal of 3991731 is 1371993.

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 3991731 - 2² = 3991727 is a prime.

It is a super-2 number, since 2×3991731² = 31867832752722, which contains 22 as substring.

It is a D-number.

It is a junction number, because it is equal to n+sod(n) for n = 3991692 and 3991701.

It is not an unprimeable number, because it can be changed into a prime (3991711) 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 3 ways as a sum of consecutive naturals, for example, 665286 + ... + 665291.

It is an arithmetic number, because the mean of its divisors is an integer number (1330578).

Almost surely, 2^3991731 is an apocalyptic number.

3991731 is a deficient number, since it is larger than the sum of its proper divisors (1330581).

3991731 is a wasteful number, since it uses less digits than its factorization.

3991731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1330580.

The product of its digits is 5103, while the sum is 33.

The square root of 3991731 is about 1997.9316805136. The cubic root of 3991731 is about 158.6306445738.

The spelling of 3991731 in words is "three million, nine hundred ninety-one thousand, seven hundred thirty-one".