3991993 has 2 divisors, whose sum is σ = 3991994. Its totient is φ = 3991992.

The previous prime is 3991973. The next prime is 3991997.

3991993 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2985984 + 1006009 = 1728^2 + 1003^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 3991993 - 2⁵ = 3991961 is a prime.

It is a super-2 number, since 2×3991993² = 31872016224098, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (3991997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995996 + 1995997.

It is an arithmetic number, because the mean of its divisors is an integer number (1995997).

Almost surely, 2^3991993 is an apocalyptic number.

It is an amenable number.

3991993 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991993 is an equidigital number, since it uses as much as digits as its factorization.

3991993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 59049, while the sum is 43.

The square root of 3991993 is about 1997.9972472454. The cubic root of 3991993 is about 158.6341151082.

The spelling of 3991993 in words is "three million, nine hundred ninety-one thousand, nine hundred ninety-three".