3901991 has 4 divisors (see below), whose sum is σ = 3927984. Its totient is φ = 3876000.

The previous prime is 3901981. The next prime is 3901999. The reversal of 3901991 is 1991093.

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 3901991 - 2¹⁸ = 3639847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3901999) 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, 12770 + ... + 13071.

It is an arithmetic number, because the mean of its divisors is an integer number (981996).

Almost surely, 2^3901991 is an apocalyptic number.

3901991 is a deficient number, since it is larger than the sum of its proper divisors (25993).

3901991 is a wasteful number, since it uses less digits than its factorization.

3901991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25992.

The product of its (nonzero) digits is 2187, while the sum is 32.

The square root of 3901991 is about 1975.3457925133. The cubic root of 3901991 is about 157.4328730489.

The spelling of 3901991 in words is "three million, nine hundred one thousand, nine hundred ninety-one".