3991261 has 2 divisors, whose sum is σ = 3991262. Its totient is φ = 3991260.

The previous prime is 3991237. The next prime is 3991279. The reversal of 3991261 is 1621993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3980025 + 11236 = 1995^2 + 106^2 .

It is an emirp because it is prime and its reverse (1621993) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 3991261 - 2¹³ = 3983069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3991961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995630 + 1995631.

It is an arithmetic number, because the mean of its divisors is an integer number (1995631).

Almost surely, 2^3991261 is an apocalyptic number.

It is an amenable number.

3991261 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991261 is an equidigital number, since it uses as much as digits as its factorization.

3991261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2916, while the sum is 31.

The square root of 3991261 is about 1997.8140554116. The cubic root of 3991261 is about 158.6244184254.

The spelling of 3991261 in words is "three million, nine hundred ninety-one thousand, two hundred sixty-one".