3991649 has 2 divisors, whose sum is σ = 3991650. Its totient is φ = 3991648.

The previous prime is 3991639. The next prime is 3991667. The reversal of 3991649 is 9461993.

3991649 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3972049 + 19600 = 1993^2 + 140^2 .

It is a cyclic number.

It is not a de Polignac number, because 3991649 - 2¹⁶ = 3926113 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (3991609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995824 + 1995825.

It is an arithmetic number, because the mean of its divisors is an integer number (1995825).

Almost surely, 2^3991649 is an apocalyptic number.

It is an amenable number.

3991649 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991649 is an equidigital number, since it uses as much as digits as its factorization.

3991649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52488, while the sum is 41.

The square root of 3991649 is about 1997.9111591860. The cubic root of 3991649 is about 158.6295583448.

It can be divided in two parts, 399 and 1649, that added together give a 11-th power (2048 = 2¹¹).

The spelling of 3991649 in words is "three million, nine hundred ninety-one thousand, six hundred forty-nine".