638778920 has 64 divisors (see below), whose sum is σ = 1551931920. Its totient is φ = 235229184.

The previous prime is 638778919. The next prime is 638778923. The reversal of 638778920 is 29877836.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 3844 + 638775076 = 62^2 + 25274^2 .

It is not an unprimeable number, because it can be changed into a prime (638778923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 223742 + ... + 226578.

Almost surely, 2^638778920 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 638778920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (775965960).

638778920 is an abundant number, since it is smaller than the sum of its proper divisors (913153000).

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

638778920 is a wasteful number, since it uses less digits than its factorization.

638778920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3294 (or 3290 counting only the distinct ones).

The product of its (nonzero) digits is 1016064, while the sum is 50.

The square root of 638778920 is about 25274.0760464156. The cubic root of 638778920 is about 861.2254568500.

The spelling of 638778920 in words is "six hundred thirty-eight million, seven hundred seventy-eight thousand, nine hundred twenty".