638441778 has 48 divisors (see below), whose sum is σ = 1397130336. Its totient is φ = 194388480.

The previous prime is 638441777. The next prime is 638441779. The reversal of 638441778 is 877144836.

It is an interprime number because it is at equal distance from previous prime (638441777) and next prime (638441779).

It is not an unprimeable number, because it can be changed into a prime (638441777) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 95113 + ... + 101603.

It is an arithmetic number, because the mean of its divisors is an integer number (29106882).

Almost surely, 2^638441778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638441778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (698565168).

638441778 is an abundant number, since it is smaller than the sum of its proper divisors (758688558).

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

638441778 is a wasteful number, since it uses less digits than its factorization.

638441778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6619 (or 6606 counting only the distinct ones).

The product of its digits is 903168, while the sum is 48.

The square root of 638441778 is about 25267.4054465432. The cubic root of 638441778 is about 861.0739143987.

The spelling of 638441778 in words is "six hundred thirty-eight million, four hundred forty-one thousand, seven hundred seventy-eight".