639820440 has 576 divisors, whose sum is σ = 2688940800. Its totient is φ = 130927104.

The previous prime is 639820429. The next prime is 639820451. The reversal of 639820440 is 44028936.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (639820429) and next prime (639820451).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 639820395 and 639820404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 7708639 + ... + 7708721.

It is an arithmetic number, because the mean of its divisors is an integer number (4668300).

Almost surely, 2^639820440 is an apocalyptic number.

639820440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639820440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1344470400).

639820440 is an abundant number, since it is smaller than the sum of its proper divisors (2049120360).

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

639820440 is a wasteful number, since it uses less digits than its factorization.

639820440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 639820440 is about 25294.6721662883. The cubic root of 639820440 is about 861.6932746633.

The spelling of 639820440 in words is "six hundred thirty-nine million, eight hundred twenty thousand, four hundred forty".