3991191 has 4 divisors (see below), whose sum is σ = 5321592. Its totient is φ = 2660792.

The previous prime is 3991189. The next prime is 3991199. The reversal of 3991191 is 1911993.

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 3991191 - 2¹ = 3991189 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991199) 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, 665196 + ... + 665201.

It is an arithmetic number, because the mean of its divisors is an integer number (1330398).

Almost surely, 2^3991191 is an apocalyptic number.

3991191 is a deficient number, since it is larger than the sum of its proper divisors (1330401).

3991191 is a wasteful number, since it uses less digits than its factorization.

3991191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1330400.

The product of its digits is 2187, while the sum is 33.

The square root of 3991191 is about 1997.7965361868. The cubic root of 3991191 is about 158.6234910848.

The spelling of 3991191 in words is "three million, nine hundred ninety-one thousand, one hundred ninety-one".