638268509 has 2 divisors, whose sum is σ = 638268510. Its totient is φ = 638268508.

The previous prime is 638268503. The next prime is 638268551. The reversal of 638268509 is 905862836.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 401200900 + 237067609 = 20030^2 + 15397^2 .

It is a cyclic number.

It is not a de Polignac number, because 638268509 - 2⁴ = 638268493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638268503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319134254 + 319134255.

It is an arithmetic number, because the mean of its divisors is an integer number (319134255).

Almost surely, 2^638268509 is an apocalyptic number.

It is an amenable number.

638268509 is a deficient number, since it is larger than the sum of its proper divisors (1).

638268509 is an equidigital number, since it uses as much as digits as its factorization.

638268509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 622080, while the sum is 47.

The square root of 638268509 is about 25263.9765080638. The cubic root of 638268509 is about 860.9960107065.

The spelling of 638268509 in words is "six hundred thirty-eight million, two hundred sixty-eight thousand, five hundred nine".