638984789 has 2 divisors, whose sum is σ = 638984790. Its totient is φ = 638984788.

The previous prime is 638984779. The next prime is 638984791. The reversal of 638984789 is 987489836.

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., 529782289 + 109202500 = 23017^2 + 10450^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638984789 is a prime.

Together with 638984791, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638984719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319492394 + 319492395.

It is an arithmetic number, because the mean of its divisors is an integer number (319492395).

Almost surely, 2^638984789 is an apocalyptic number.

It is an amenable number.

638984789 is a deficient number, since it is larger than the sum of its proper divisors (1).

638984789 is an equidigital number, since it uses as much as digits as its factorization.

638984789 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20901888, while the sum is 62.

The square root of 638984789 is about 25278.1484488085. The cubic root of 638984789 is about 861.3179669890.

The spelling of 638984789 in words is "six hundred thirty-eight million, nine hundred eighty-four thousand, seven hundred eighty-nine".