639786438 has 56 divisors (see below), whose sum is σ = 1449816408. Its totient is φ = 211639392.

The previous prime is 639786391. The next prime is 639786529. The reversal of 639786438 is 834687936.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 198145 + ... + 201347.

Almost surely, 2^639786438 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639786438, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (724908204).

639786438 is an abundant number, since it is smaller than the sum of its proper divisors (810029970).

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

639786438 is a wasteful number, since it uses less digits than its factorization.

639786438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3360 (or 3345 counting only the distinct ones).

The product of its digits is 5225472, while the sum is 54.

The square root of 639786438 is about 25294.0000395351. Note that the first 4 decimals coincide. The cubic root of 639786438 is about 861.6780100610.

The spelling of 639786438 in words is "six hundred thirty-nine million, seven hundred eighty-six thousand, four hundred thirty-eight".