639782009 has 4 divisors (see below), whose sum is σ = 643707216. Its totient is φ = 635856804.

The previous prime is 639781981. The next prime is 639782023. The reversal of 639782009 is 900287936.

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 a de Polignac number, because none of the positive numbers 2^k-639782009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639782809) 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, 1962359 + ... + 1962684.

It is an arithmetic number, because the mean of its divisors is an integer number (160926804).

Almost surely, 2^639782009 is an apocalyptic number.

It is an amenable number.

639782009 is a deficient number, since it is larger than the sum of its proper divisors (3925207).

639782009 is a wasteful number, since it uses less digits than its factorization.

639782009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3925206.

The product of its (nonzero) digits is 163296, while the sum is 44.

The square root of 639782009 is about 25293.9124889765. The cubic root of 639782009 is about 861.6760216992.

The spelling of 639782009 in words is "six hundred thirty-nine million, seven hundred eighty-two thousand, nine".