638647 has 4 divisors (see below), whose sum is σ = 672280. Its totient is φ = 605016.

The previous prime is 638633. The next prime is 638663. The reversal of 638647 is 746836.

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 638647 - 2¹⁵ = 605879 is a prime.

It is a Duffinian number.

638647 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638047) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16788 + ... + 16825.

It is an arithmetic number, because the mean of its divisors is an integer number (168070).

2⁶³⁸⁶⁴⁷ is an apocalyptic number.

638647 is a deficient number, since it is larger than the sum of its proper divisors (33633).

638647 is a wasteful number, since it uses less digits than its factorization.

638647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33632.

The product of its digits is 24192, while the sum is 34.

The square root of 638647 is about 799.1539276009. The cubic root of 638647 is about 86.1166166288.

The spelling of 638647 in words is "six hundred thirty-eight thousand, six hundred forty-seven".