639788161 has 2 divisors, whose sum is σ = 639788162. Its totient is φ = 639788160.

The previous prime is 639788141. The next prime is 639788167. The reversal of 639788161 is 161887936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 321843600 + 317944561 = 17940^2 + 17831^2 .

It is a cyclic number.

It is not a de Polignac number, because 639788161 - 2⁹ = 639787649 is a prime.

It is not a weakly prime, because it can be changed into another prime (639788167) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319894080 + 319894081.

It is an arithmetic number, because the mean of its divisors is an integer number (319894081).

Almost surely, 2^639788161 is an apocalyptic number.

It is an amenable number.

639788161 is a deficient number, since it is larger than the sum of its proper divisors (1).

639788161 is an equidigital number, since it uses as much as digits as its factorization.

639788161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 49.

The square root of 639788161 is about 25294.0340989728. The cubic root of 639788161 is about 861.6787835847.

The spelling of 639788161 in words is "six hundred thirty-nine million, seven hundred eighty-eight thousand, one hundred sixty-one".