639664128 has 160 divisors (see below), whose sum is σ = 1918995870. Its totient is φ = 212336640.

The previous prime is 639664121. The next prime is 639664147. The reversal of 639664128 is 821466936.

639664128 is a `hidden beast` number, since 639 + 6 + 6 + 4 + 1 + 2 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 479084544 + 160579584 = 21888^2 + 12672^2 .

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (639664121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 2654088 + ... + 2654328.

Almost surely, 2^639664128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639664128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (959497935).

639664128 is an abundant number, since it is smaller than the sum of its proper divisors (1279331742).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639664128 is an frugal number, since it uses more digits than its factorization.

639664128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283 (or 246 counting only the distinct ones).

The product of its digits is 373248, while the sum is 45.

The square root of 639664128 is about 25291.5821569154. The cubic root of 639664128 is about 861.6230966566.

The spelling of 639664128 in words is "six hundred thirty-nine million, six hundred sixty-four thousand, one hundred twenty-eight".