3990781 has 4 divisors (see below), whose sum is σ = 3995964. Its totient is φ = 3985600.

The previous prime is 3990773. The next prime is 3990827. The reversal of 3990781 is 1870993.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3404025 + 586756 = 1845^2 + 766^2 .

It is a cyclic number.

It is not a de Polignac number, because 3990781 - 2³ = 3990773 is a prime.

It is a super-2 number, since 2×3990781² = 31852665979922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 3990781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3990731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1180 + ... + 3061.

It is an arithmetic number, because the mean of its divisors is an integer number (998991).

Almost surely, 2^3990781 is an apocalyptic number.

It is an amenable number.

3990781 is a deficient number, since it is larger than the sum of its proper divisors (5183).

3990781 is an equidigital number, since it uses as much as digits as its factorization.

3990781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5182.

The product of its (nonzero) digits is 13608, while the sum is 37.

The square root of 3990781 is about 1997.6939204993. The cubic root of 3990781 is about 158.6180593012.

The spelling of 3990781 in words is "three million, nine hundred ninety thousand, seven hundred eighty-one".