3981805 has 4 divisors (see below), whose sum is σ = 4778172. Its totient is φ = 3185440.

The previous prime is 3981767. The next prime is 3981821. The reversal of 3981805 is 5081893.

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 499849 + 3481956 = 707^2 + 1866^2 .

It is not a de Polignac number, because 3981805 - 2¹⁵ = 3949037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 398176 + ... + 398185.

It is an arithmetic number, because the mean of its divisors is an integer number (1194543).

Almost surely, 2^3981805 is an apocalyptic number.

It is an amenable number.

3981805 is a deficient number, since it is larger than the sum of its proper divisors (796367).

3981805 is an equidigital number, since it uses as much as digits as its factorization.

3981805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 796366.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 3981805 is about 1995.4460654200. The cubic root of 3981805 is about 158.4990496415.

The spelling of 3981805 in words is "three million, nine hundred eighty-one thousand, eight hundred five".