3981661 has 4 divisors (see below), whose sum is σ = 4018300. Its totient is φ = 3945024.

The previous prime is 3981647. The next prime is 3981683. The reversal of 3981661 is 1661893.

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 2910436 + 1071225 = 1706^2 + 1035^2 .

It is a cyclic number.

It is not a de Polignac number, because 3981661 - 2⁵ = 3981629 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 (3981641) 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, 18156 + ... + 18373.

It is an arithmetic number, because the mean of its divisors is an integer number (1004575).

Almost surely, 2^3981661 is an apocalyptic number.

It is an amenable number.

3981661 is a deficient number, since it is larger than the sum of its proper divisors (36639).

3981661 is a wasteful number, since it uses less digits than its factorization.

3981661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36638.

The product of its digits is 7776, while the sum is 34.

The square root of 3981661 is about 1995.4099829358. The cubic root of 3981661 is about 158.4971389387.

The spelling of 3981661 in words is "three million, nine hundred eighty-one thousand, six hundred sixty-one".