3991961 has 2 divisors, whose sum is σ = 3991962. Its totient is φ = 3991960.

The previous prime is 3991943. The next prime is 3991973. The reversal of 3991961 is 1691993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3924361 + 67600 = 1981^2 + 260^2 .

It is a cyclic number.

It is not a de Polignac number, because 3991961 - 2¹⁴ = 3975577 is a prime.

It is not a weakly prime, because it can be changed into another prime (3991261) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995980 + 1995981.

It is an arithmetic number, because the mean of its divisors is an integer number (1995981).

Almost surely, 2^3991961 is an apocalyptic number.

It is an amenable number.

3991961 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991961 is an equidigital number, since it uses as much as digits as its factorization.

3991961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13122, while the sum is 38.

The square root of 3991961 is about 1997.9892392103. The cubic root of 3991961 is about 158.6336912343.

Subtracting from 3991961 its reverse (1691993), we obtain a cube (2299968 = 132³).

The spelling of 3991961 in words is "three million, nine hundred ninety-one thousand, nine hundred sixty-one".