3961755721 has 16 divisors (see below), whose sum is σ = 5199298560. Its totient is φ = 2924603280.

The previous prime is 3961755709. The next prime is 3961755731. The reversal of 3961755721 is 1275571693.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 3961755721 - 2⁵ = 3961755689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3961755731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1352521 + ... + 1355446.

It is an arithmetic number, because the mean of its divisors is an integer number (324956160).

Almost surely, 2^3961755721 is an apocalyptic number.

It is an amenable number.

3961755721 is a deficient number, since it is larger than the sum of its proper divisors (1237542839).

3961755721 is a wasteful number, since it uses less digits than its factorization.

3961755721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2708004.

The product of its digits is 396900, while the sum is 46.

The square root of 3961755721 is about 62942.4794633958. The cubic root of 3961755721 is about 1582.3257582974.

The spelling of 3961755721 in words is "three billion, nine hundred sixty-one million, seven hundred fifty-five thousand, seven hundred twenty-one".