3991997 has 2 divisors, whose sum is σ = 3991998. Its totient is φ = 3991996.

The previous prime is 3991993. The next prime is 3992011. The reversal of 3991997 is 7991993.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3334276 + 657721 = 1826^2 + 811^2 .

It is an emirp because it is prime and its reverse (7991993) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3991997 - 2² = 3991993 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3991993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995998 + 1995999.

It is an arithmetic number, because the mean of its divisors is an integer number (1995999).

Almost surely, 2^3991997 is an apocalyptic number.

It is an amenable number.

3991997 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991997 is an equidigital number, since it uses as much as digits as its factorization.

3991997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 137781, while the sum is 47.

The square root of 3991997 is about 1997.9982482475. The cubic root of 3991997 is about 158.6341680923.

The spelling of 3991997 in words is "three million, nine hundred ninety-one thousand, nine hundred ninety-seven".