3928961821 has 6 divisors (see below), whose sum is σ = 4107213950. Its totient is φ = 3758136888.

The previous prime is 3928961819. The next prime is 3928961837. The reversal of 3928961821 is 1281698293.

It can be written as a sum of positive squares in only one way, i.e., 2373053796 + 1555908025 = 48714^2 + 39445^2 .

It is not a de Polignac number, because 3928961821 - 2¹ = 3928961819 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 (3928961021) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3713046 + ... + 3714103.

Almost surely, 2^3928961821 is an apocalyptic number.

It is an amenable number.

3928961821 is a deficient number, since it is larger than the sum of its proper divisors (178252129).

3928961821 is an equidigital number, since it uses as much as digits as its factorization.

3928961821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7427195 (or 7427172 counting only the distinct ones).

The product of its digits is 373248, while the sum is 49.

The square root of 3928961821 is about 62681.4312296712. The cubic root of 3928961821 is about 1577.9476933373.

The spelling of 3928961821 in words is "three billion, nine hundred twenty-eight million, nine hundred sixty-one thousand, eight hundred twenty-one".