638644673 has 2 divisors, whose sum is σ = 638644674. Its totient is φ = 638644672.

The previous prime is 638644667. The next prime is 638644681. The reversal of 638644673 is 376446836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 321377329 + 317267344 = 17927^2 + 17812^2 .

It is a cyclic number.

It is not a de Polignac number, because 638644673 - 2¹² = 638640577 is a prime.

It is not a weakly prime, because it can be changed into another prime (638644693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319322336 + 319322337.

It is an arithmetic number, because the mean of its divisors is an integer number (319322337).

Almost surely, 2^638644673 is an apocalyptic number.

It is an amenable number.

638644673 is a deficient number, since it is larger than the sum of its proper divisors (1).

638644673 is an equidigital number, since it uses as much as digits as its factorization.

638644673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 47.

The square root of 638644673 is about 25271.4200827733. The cubic root of 638644673 is about 861.1651203598.

The spelling of 638644673 in words is "six hundred thirty-eight million, six hundred forty-four thousand, six hundred seventy-three".