638947 has 4 divisors (see below), whose sum is σ = 641056. Its totient is φ = 636840.

The previous prime is 638933. The next prime is 638959. The reversal of 638947 is 749836.

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 638947 - 2⁷ = 638819 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638977) 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, 504 + ... + 1237.

It is an arithmetic number, because the mean of its divisors is an integer number (160264).

2⁶³⁸⁹⁴⁷ is an apocalyptic number.

638947 is the 462-nd hex number.

638947 is a deficient number, since it is larger than the sum of its proper divisors (2109).

638947 is a wasteful number, since it uses less digits than its factorization.

638947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2108.

The product of its digits is 36288, while the sum is 37.

The square root of 638947 is about 799.3416040718. The cubic root of 638947 is about 86.1300987458.

Subtracting 638947 from its reverse (749836), we obtain a square (110889 = 333²).

The spelling of 638947 in words is "six hundred thirty-eight thousand, nine hundred forty-seven".