3999391 has 4 divisors (see below), whose sum is σ = 4362984. Its totient is φ = 3635800.

The previous prime is 3999389. The next prime is 3999421. The reversal of 3999391 is 1939993.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 3999391 - 2¹ = 3999389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3999311) 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 in 3 ways as a sum of consecutive naturals, for example, 181780 + ... + 181801.

It is an arithmetic number, because the mean of its divisors is an integer number (1090746).

Almost surely, 2^3999391 is an apocalyptic number.

3999391 is a deficient number, since it is larger than the sum of its proper divisors (363593).

3999391 is a wasteful number, since it uses less digits than its factorization.

3999391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363592.

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

The square root of 3999391 is about 1999.8477442045. The cubic root of 3999391 is about 158.7320487276.

It can be divided in two parts, 39993 and 91, that multiplied together give a palindrome (3639363).

The spelling of 3999391 in words is "three million, nine hundred ninety-nine thousand, three hundred ninety-one".