3921121665 has 24 divisors (see below), whose sum is σ = 6828838848. Its totient is φ = 2081348640.

The previous prime is 3921121649. The next prime is 3921121681. The reversal of 3921121665 is 5661211293.

3921121665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (3921121649) and next prime (3921121681).

It is not a de Polignac number, because 3921121665 - 2⁴ = 3921121649 is a prime.

It is a super-2 number, since 2×3921121665² = 30750390223464744450, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 196989 + ... + 215978.

It is an arithmetic number, because the mean of its divisors is an integer number (284534952).

Almost surely, 2^3921121665 is an apocalyptic number.

It is an amenable number.

3921121665 is a deficient number, since it is larger than the sum of its proper divisors (2907717183).

3921121665 is a wasteful number, since it uses less digits than its factorization.

3921121665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413189 (or 413186 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 3921121665 is about 62618.8602978368. The cubic root of 3921121665 is about 1576.8974079017.

The spelling of 3921121665 in words is "three billion, nine hundred twenty-one million, one hundred twenty-one thousand, six hundred sixty-five".