3991667 has 2 divisors, whose sum is σ = 3991668. Its totient is φ = 3991666.

The previous prime is 3991649. The next prime is 3991679. The reversal of 3991667 is 7661993.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (7661993) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3991667 is a prime.

It is not a weakly prime, because it can be changed into another prime (3991607) 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, 1995833 + 1995834.

It is an arithmetic number, because the mean of its divisors is an integer number (1995834).

Almost surely, 2^3991667 is an apocalyptic number.

3991667 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991667 is an equidigital number, since it uses as much as digits as its factorization.

3991667 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 61236, while the sum is 41.

The square root of 3991667 is about 1997.9156638857. The cubic root of 3991667 is about 158.6297967866.

The spelling of 3991667 in words is "three million, nine hundred ninety-one thousand, six hundred sixty-seven".