639720985 has 8 divisors (see below), whose sum is σ = 767804040. Its totient is φ = 511684224.

The previous prime is 639720979. The next prime is 639720989. The reversal of 639720985 is 589027936.

It can be written as a sum of positive squares in 4 ways, for example, as 225720576 + 414000409 = 15024^2 + 20347^2 .

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 639720985 - 2¹³ = 639712793 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639720989) 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, 38661 + ... + 52669.

It is an arithmetic number, because the mean of its divisors is an integer number (95975505).

Almost surely, 2^639720985 is an apocalyptic number.

It is an amenable number.

639720985 is a deficient number, since it is larger than the sum of its proper divisors (128083055).

639720985 is a wasteful number, since it uses less digits than its factorization.

639720985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23147.

The product of its (nonzero) digits is 816480, while the sum is 49.

The square root of 639720985 is about 25292.7061620539. The cubic root of 639720985 is about 861.6486245604.

The spelling of 639720985 in words is "six hundred thirty-nine million, seven hundred twenty thousand, nine hundred eighty-five".