639777169 has 2 divisors, whose sum is σ = 639777170. Its totient is φ = 639777168.

The previous prime is 639777097. The next prime is 639777181. The reversal of 639777169 is 961777936.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 579124225 + 60652944 = 24065^2 + 7788^2 .

It is a cyclic number.

It is not a de Polignac number, because 639777169 - 2¹⁹ = 639252881 is a prime.

It is a super-2 number, since 2×639777169² = 818629651947309122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (639777199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319888584 + 319888585.

It is an arithmetic number, because the mean of its divisors is an integer number (319888585).

Almost surely, 2^639777169 is an apocalyptic number.

It is an amenable number.

639777169 is a deficient number, since it is larger than the sum of its proper divisors (1).

639777169 is an equidigital number, since it uses as much as digits as its factorization.

639777169 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3000564, while the sum is 55.

The square root of 639777169 is about 25293.8168136009. The cubic root of 639777169 is about 861.6738488120.

The spelling of 639777169 in words is "six hundred thirty-nine million, seven hundred seventy-seven thousand, one hundred sixty-nine".