3975393957921 has 9 divisors (see below), whose sum is σ = 5742244356979. Its totient is φ = 2650258650936.

The previous prime is 3975393957907. The next prime is 3975393957929. The reversal of 3975393957921 is 1297593935793.

The square root of 3975393957921 is 1993839.

It is a perfect power (a square), and thus also a powerful number.

3975393957921 is a `hidden beast` number, since 3 + 9 + 7 + 539 + 39 + 57 + 9 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 107233326225 + 3868160631696 = 327465^2 + 1966764^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 3975393957921 - 2⁵ = 3975393957889 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 3975393957921.

It is not an unprimeable number, because it can be changed into a prime (3975393957929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5649211 + ... + 6313823.

Almost surely, 2^{3975393957921} is an apocalyptic number.

3975393957921 is the 1993839-th square number.

3975393957921 is the 996920-th centered octagonal number.

It is an amenable number.

3975393957921 is a deficient number, since it is larger than the sum of its proper divisors (1766850399058).

3975393957921 is an frugal number, since it uses more digits than its factorization.

3975393957921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1329232 (or 664616 counting only the distinct ones).

The product of its digits is 434010150, while the sum is 72.

The spelling of 3975393957921 in words is "three trillion, nine hundred seventy-five billion, three hundred ninety-three million, nine hundred fifty-seven thousand, nine hundred twenty-one".