638689 has 2 divisors, whose sum is σ = 638690. Its totient is φ = 638688.

The previous prime is 638669. The next prime is 638699. The reversal of 638689 is 986836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 613089 + 25600 = 783^2 + 160^2 .

It is a cyclic number.

It is not a de Polignac number, because 638689 - 2⁹ = 638177 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (638629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319344 + 319345.

It is an arithmetic number, because the mean of its divisors is an integer number (319345).

2⁶³⁸⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

638689 is a deficient number, since it is larger than the sum of its proper divisors (1).

638689 is an equidigital number, since it uses as much as digits as its factorization.

638689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 40.

The square root of 638689 is about 799.1802049601. The cubic root of 638689 is about 86.1185043793.

The spelling of 638689 in words is "six hundred thirty-eight thousand, six hundred eighty-nine".