3991365 has 24 divisors (see below), whose sum is σ = 7907328. Its totient is φ = 1824480.

The previous prime is 3991333. The next prime is 3991369. The reversal of 3991365 is 5631993.

It is not a de Polignac number, because 3991365 - 2⁵ = 3991333 is a prime.

It is an Ulam number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991369) 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 23 ways as a sum of consecutive naturals, for example, 6021 + ... + 6650.

It is an arithmetic number, because the mean of its divisors is an integer number (329472).

Almost surely, 2^3991365 is an apocalyptic number.

3991365 is a gapful number since it is divisible by the number (35) formed by its first and last digit.

It is an amenable number.

3991365 is a deficient number, since it is larger than the sum of its proper divisors (3915963).

3991365 is a wasteful number, since it uses less digits than its factorization.

3991365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12689 (or 12686 counting only the distinct ones).

The product of its digits is 21870, while the sum is 36.

The square root of 3991365 is about 1997.8400836904. The cubic root of 3991365 is about 158.6257961684.

It can be divided in two parts, 3991 and 365, that added together give a square (4356 = 66²).

The spelling of 3991365 in words is "three million, nine hundred ninety-one thousand, three hundred sixty-five".