639817 has 4 divisors (see below), whose sum is σ = 644560. Its totient is φ = 635076.

The previous prime is 639757. The next prime is 639833. The reversal of 639817 is 718936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 639817 - 2⁷ = 639689 is a prime.

It is an Ulam number.

It is a Duffinian number.

639817 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (639857) 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, 2163 + ... + 2440.

It is an arithmetic number, because the mean of its divisors is an integer number (161140).

2⁶³⁹⁸¹⁷ is an apocalyptic number.

It is an amenable number.

639817 is a deficient number, since it is larger than the sum of its proper divisors (4743).

639817 is a wasteful number, since it uses less digits than its factorization.

639817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4742.

The product of its digits is 9072, while the sum is 34.

The square root of 639817 is about 799.8856168228. The cubic root of 639817 is about 86.1691730360.

The spelling of 639817 in words is "six hundred thirty-nine thousand, eight hundred seventeen".