638635 has 4 divisors (see below), whose sum is σ = 766368. Its totient is φ = 510904.

The previous prime is 638633. The next prime is 638663. The reversal of 638635 is 536836.

638635 = T₆₅₁ + T₆₅₂ + T₆₅₃.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 638635 - 2¹ = 638633 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638597 and 638606.

It is not an unprimeable number, because it can be changed into a prime (638633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63859 + ... + 63868.

It is an arithmetic number, because the mean of its divisors is an integer number (191592).

2⁶³⁸⁶³⁵ is an apocalyptic number.

638635 is the 653-rd centered triangular number.

638635 is a deficient number, since it is larger than the sum of its proper divisors (127733).

638635 is a wasteful number, since it uses less digits than its factorization.

638635 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127732.

The product of its digits is 12960, while the sum is 31.

The square root of 638635 is about 799.1464196253. The cubic root of 638635 is about 86.1160772563.

The spelling of 638635 in words is "six hundred thirty-eight thousand, six hundred thirty-five".