3961 has 4 divisors (see below), whose sum is σ = 4212. Its totient is φ = 3712.

The previous prime is 3947. The next prime is 3967. The reversal of 3961 is 1693.

3961 = 44² + 45².

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 1936 + 2025 = 44^2 + 45^2 .

It is a cyclic number.

It is not a de Polignac number, because 3961 - 2⁵ = 3929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3967) 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, 100 + ... + 133.

It is an arithmetic number, because the mean of its divisors is an integer number (1053).

2³⁹⁶¹ is an apocalyptic number.

3961 is the 34-th nonagonal number.

3961 is the 45-th centered square number.

It is an amenable number.

3961 is a deficient number, since it is larger than the sum of its proper divisors (251).

3961 is a wasteful number, since it uses less digits than its factorization.

3961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250.

The product of its digits is 162, while the sum is 19.

The square root of 3961 is about 62.9364759102. The cubic root of 3961 is about 15.8222514021.

It can be divided in two parts, 39 and 61, that added together give a square (100 = 10²).

The spelling of 3961 in words is "three thousand, nine hundred sixty-one".