4031991 has 8 divisors (see below), whose sum is σ = 5973360. Its totient is φ = 2687976.

The previous prime is 4031987. The next prime is 4032029. The reversal of 4031991 is 1991304.

It is not a de Polignac number, because 4031991 - 2² = 4031987 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 149333 = 4031991 / (4 + 0 + 3 + 1 + 9 + 9 + 1).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4031491) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 74640 + ... + 74693.

It is an arithmetic number, because the mean of its divisors is an integer number (746670).

Almost surely, 2^4031991 is an apocalyptic number.

4031991 is a deficient number, since it is larger than the sum of its proper divisors (1941369).

4031991 is a wasteful number, since it uses less digits than its factorization.

4031991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149342 (or 149336 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 4031991 is about 2007.9818226269. The cubic root of 4031991 is about 159.1621698914.

The spelling of 4031991 in words is "four million, thirty-one thousand, nine hundred ninety-one".