638644917 has 8 divisors (see below), whose sum is σ = 859957920. Its totient is φ = 421547600.

The previous prime is 638644879. The next prime is 638644943. The reversal of 638644917 is 719446836.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638644917 - 2¹¹ = 638642869 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638644997) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1053567 + ... + 1054172.

It is an arithmetic number, because the mean of its divisors is an integer number (107494740).

Almost surely, 2^638644917 is an apocalyptic number.

It is an amenable number.

638644917 is a deficient number, since it is larger than the sum of its proper divisors (221313003).

638644917 is a wasteful number, since it uses less digits than its factorization.

638644917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2107843.

The product of its digits is 870912, while the sum is 48.

The square root of 638644917 is about 25271.4249103607. The cubic root of 638644917 is about 861.1652300317.

The spelling of 638644917 in words is "six hundred thirty-eight million, six hundred forty-four thousand, nine hundred seventeen".