638551340 has 72 divisors (see below), whose sum is σ = 1565197200. Its totient is φ = 218187648.

The previous prime is 638551327. The next prime is 638551349. The reversal of 638551340 is 43155836.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 638551340.

It is not an unprimeable number, because it can be changed into a prime (638551349) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 341087 + ... + 342953.

It is an arithmetic number, because the mean of its divisors is an integer number (21738850).

Almost surely, 2^638551340 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 638551340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (782598600).

638551340 is an abundant number, since it is smaller than the sum of its proper divisors (926645860).

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

638551340 is a wasteful number, since it uses less digits than its factorization.

638551340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2239 (or 2230 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 35.

The square root of 638551340 is about 25269.5734036014. The cubic root of 638551340 is about 861.1231674328.

The spelling of 638551340 in words is "six hundred thirty-eight million, five hundred fifty-one thousand, three hundred forty".