639979705 has 8 divisors (see below), whose sum is σ = 813150792. Its totient is φ = 481867008.

The previous prime is 639979699. The next prime is 639979709. The reversal of 639979705 is 507979936.

It can be written as a sum of positive squares in 4 ways, for example, as 345067776 + 294911929 = 18576^2 + 17173^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639979705 - 2¹³ = 639971513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639979709) 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 7 ways as a sum of consecutive naturals, for example, 3764502 + ... + 3764671.

It is an arithmetic number, because the mean of its divisors is an integer number (101643849).

Almost surely, 2^639979705 is an apocalyptic number.

It is an amenable number.

639979705 is a deficient number, since it is larger than the sum of its proper divisors (173171087).

639979705 is a wasteful number, since it uses less digits than its factorization.

639979705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7529195.

The product of its (nonzero) digits is 3214890, while the sum is 55.

The square root of 639979705 is about 25297.8201630101. The cubic root of 639979705 is about 861.7647666973.

The spelling of 639979705 in words is "six hundred thirty-nine million, nine hundred seventy-nine thousand, seven hundred five".