638428897 has 8 divisors (see below), whose sum is σ = 676204200. Its totient is φ = 600678144.

The previous prime is 638428891. The next prime is 638428919. The reversal of 638428897 is 798824836.

It can be written as a sum of positive squares in 4 ways, for example, as 332843536 + 305585361 = 18244^2 + 17481^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638428897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638428891) 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, 99379 + ... + 105607.

It is an arithmetic number, because the mean of its divisors is an integer number (84525525).

Almost surely, 2^638428897 is an apocalyptic number.

It is an amenable number.

638428897 is a deficient number, since it is larger than the sum of its proper divisors (37775303).

638428897 is a wasteful number, since it uses less digits than its factorization.

638428897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12275.

The product of its digits is 4644864, while the sum is 55.

The square root of 638428897 is about 25267.1505516550. The cubic root of 638428897 is about 861.0681234411.

The spelling of 638428897 in words is "six hundred thirty-eight million, four hundred twenty-eight thousand, eight hundred ninety-seven".