3977638921 has 2 divisors, whose sum is σ = 3977638922. Its totient is φ = 3977638920.

The previous prime is 3977638913. The next prime is 3977638949. The reversal of 3977638921 is 1298367793.

It is a happy number.

3977638921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2568462400 + 1409176521 = 50680^2 + 37539^2 .

It is a cyclic number.

It is not a de Polignac number, because 3977638921 - 2³ = 3977638913 is a prime.

It is a super-2 number, since 2×3977638921² = 31643222771708088482, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (3977638421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1988819460 + 1988819461.

It is an arithmetic number, because the mean of its divisors is an integer number (1988819461).

Almost surely, 2^3977638921 is an apocalyptic number.

It is an amenable number.

3977638921 is a deficient number, since it is larger than the sum of its proper divisors (1).

3977638921 is an equidigital number, since it uses as much as digits as its factorization.

3977638921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3429216, while the sum is 55.

The square root of 3977638921 is about 63068.5255971630. The cubic root of 3977638921 is about 1584.4375227521.

The spelling of 3977638921 in words is "three billion, nine hundred seventy-seven million, six hundred thirty-eight thousand, nine hundred twenty-one".