639318585805 has 4 divisors (see below), whose sum is σ = 767182302972. Its totient is φ = 511454868640.

The previous prime is 639318585803. The next prime is 639318585839. The reversal of 639318585805 is 508585813936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 94174106884 + 545144478921 = 306878^2 + 738339^2 .

It is not a de Polignac number, because 639318585805 - 2¹ = 639318585803 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639318585803) 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, 63931858576 + ... + 63931858585.

It is an arithmetic number, because the mean of its divisors is an integer number (191795575743).

Almost surely, 2^639318585805 is an apocalyptic number.

It is an amenable number.

639318585805 is a deficient number, since it is larger than the sum of its proper divisors (127863717167).

639318585805 is a wasteful number, since it uses less digits than its factorization.

639318585805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127863717166.

The product of its (nonzero) digits is 31104000, while the sum is 61.

The spelling of 639318585805 in words is "six hundred thirty-nine billion, three hundred eighteen million, five hundred eighty-five thousand, eight hundred five".