3921991 has 2 divisors, whose sum is σ = 3921992. Its totient is φ = 3921990.

The previous prime is 3921971. The next prime is 3921997. The reversal of 3921991 is 1991293.

It is a strong prime.

It is an emirp because it is prime and its reverse (1991293) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3921991 - 2⁵ = 3921959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3921997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1960995 + 1960996.

It is an arithmetic number, because the mean of its divisors is an integer number (1960996).

Almost surely, 2^3921991 is an apocalyptic number.

3921991 is a deficient number, since it is larger than the sum of its proper divisors (1).

3921991 is an equidigital number, since it uses as much as digits as its factorization.

3921991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4374, while the sum is 34.

The square root of 3921991 is about 1980.4017269231. The cubic root of 3921991 is about 157.7013935002.

The spelling of 3921991 in words is "three million, nine hundred twenty-one thousand, nine hundred ninety-one".