638265891 has 8 divisors (see below), whose sum is σ = 853044304. Its totient is φ = 424499040.

The previous prime is 638265857. The next prime is 638265949. The reversal of 638265891 is 198562836.

It is a happy number.

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

It is not a de Polignac number, because 638265891 - 2⁶ = 638265827 is a prime.

It is a super-2 number, since 2×638265891² = 814766695228047762, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 638265891.

It is not an unprimeable number, because it can be changed into a prime (638265811) 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, 251416 + ... + 253941.

It is an arithmetic number, because the mean of its divisors is an integer number (106630538).

Almost surely, 2^638265891 is an apocalyptic number.

638265891 is a deficient number, since it is larger than the sum of its proper divisors (214778413).

638265891 is a wasteful number, since it uses less digits than its factorization.

638265891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 505781.

The product of its digits is 622080, while the sum is 48.

The square root of 638265891 is about 25263.9246951063. The cubic root of 638265891 is about 860.9948335161.

The spelling of 638265891 in words is "six hundred thirty-eight million, two hundred sixty-five thousand, eight hundred ninety-one".