639756389 has 2 divisors, whose sum is σ = 639756390. Its totient is φ = 639756388.

The previous prime is 639756371. The next prime is 639756407. The reversal of 639756389 is 983657936.

It is a balanced prime because it is at equal distance from previous prime (639756371) and next prime (639756407).

It can be written as a sum of positive squares in only one way, i.e., 593312164 + 46444225 = 24358^2 + 6815^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639756389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639756319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319878194 + 319878195.

It is an arithmetic number, because the mean of its divisors is an integer number (319878195).

Almost surely, 2^639756389 is an apocalyptic number.

It is an amenable number.

639756389 is a deficient number, since it is larger than the sum of its proper divisors (1).

639756389 is an equidigital number, since it uses as much as digits as its factorization.

639756389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7348320, while the sum is 56.

The square root of 639756389 is about 25293.4060379380. The cubic root of 639756389 is about 861.6645196386.

The spelling of 639756389 in words is "six hundred thirty-nine million, seven hundred fifty-six thousand, three hundred eighty-nine".