639533440 has 256 divisors, whose sum is σ = 1919232000. Its totient is φ = 198402048.

The previous prime is 639533437. The next prime is 639533443. The reversal of 639533440 is 44335936.

It is an interprime number because it is at equal distance from previous prime (639533437) and next prime (639533443).

It is a self number, because there is not a number n which added to its sum of digits gives 639533440.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639533443) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4600891 + ... + 4601029.

It is an arithmetic number, because the mean of its divisors is an integer number (7497000).

Almost surely, 2^639533440 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 639533440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (959616000).

639533440 is an abundant number, since it is smaller than the sum of its proper divisors (1279698560).

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

639533440 is a wasteful number, since it uses less digits than its factorization.

639533440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257 (or 245 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 37.

The square root of 639533440 is about 25288.9983985131. The cubic root of 639533440 is about 861.5644140534.

The spelling of 639533440 in words is "six hundred thirty-nine million, five hundred thirty-three thousand, four hundred forty".