638849689 has 2 divisors, whose sum is σ = 638849690. Its totient is φ = 638849688.

The previous prime is 638849683. The next prime is 638849723. The reversal of 638849689 is 986948836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 595750464 + 43099225 = 24408^2 + 6565^2 .

It is a cyclic number.

It is not a de Polignac number, because 638849689 - 2¹⁵ = 638816921 is a prime.

It is not a weakly prime, because it can be changed into another prime (638849683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319424844 + 319424845.

It is an arithmetic number, because the mean of its divisors is an integer number (319424845).

Almost surely, 2^638849689 is an apocalyptic number.

It is an amenable number.

638849689 is a deficient number, since it is larger than the sum of its proper divisors (1).

638849689 is an equidigital number, since it uses as much as digits as its factorization.

638849689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17915904, while the sum is 61.

The square root of 638849689 is about 25275.4760390383. The cubic root of 638849689 is about 861.2572601401.

The spelling of 638849689 in words is "six hundred thirty-eight million, eight hundred forty-nine thousand, six hundred eighty-nine".