3991931 has 4 divisors (see below), whose sum is σ = 3999000. Its totient is φ = 3984864.

The previous prime is 3991891. The next prime is 3991943. The reversal of 3991931 is 1391993.

It is a happy number.

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 3991931 - 2¹⁰ = 3990907 is a prime.

It is a super-2 number, since 2×3991931² = 31871026217522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 3991891 and 3991900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991961) 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, 2606 + ... + 3843.

It is an arithmetic number, because the mean of its divisors is an integer number (999750).

Almost surely, 2^3991931 is an apocalyptic number.

3991931 is a deficient number, since it is larger than the sum of its proper divisors (7069).

3991931 is an equidigital number, since it uses as much as digits as its factorization.

3991931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7068.

The product of its digits is 6561, while the sum is 35.

The square root of 3991931 is about 1997.9817316482. The cubic root of 3991931 is about 158.6332938505.

The spelling of 3991931 in words is "three million, nine hundred ninety-one thousand, nine hundred thirty-one".