638242140 has 96 divisors (see below), whose sum is σ = 1846333440. Its totient is φ = 164640256.

The previous prime is 638242133. The next prime is 638242141. The reversal of 638242140 is 41242836.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 638242098 and 638242107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638242141) 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, 249709 + ... + 252251.

It is an arithmetic number, because the mean of its divisors is an integer number (19232640).

Almost surely, 2^638242140 is an apocalyptic number.

638242140 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 638242140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (923166720).

638242140 is an abundant number, since it is smaller than the sum of its proper divisors (1208091300).

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

638242140 is a wasteful number, since it uses less digits than its factorization.

638242140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2691 (or 2689 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 30.

The square root of 638242140 is about 25263.4546331257. The cubic root of 638242140 is about 860.9841536714.

Adding to 638242140 its reverse (41242836), we get a palindrome (679484976).

The spelling of 638242140 in words is "six hundred thirty-eight million, two hundred forty-two thousand, one hundred forty".