638945280 has 192 divisors, whose sum is σ = 2272233600. Its totient is φ = 170311680.

The previous prime is 638945261. The next prime is 638945287. The reversal of 638945280 is 82549836.

638945280 is a `hidden beast` number, since 6 + 38 + 94 + 528 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (638945287) 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, 275325 + ... + 277635.

It is an arithmetic number, because the mean of its divisors is an integer number (11834550).

Almost surely, 2^638945280 is an apocalyptic number.

638945280 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 638945280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1136116800).

638945280 is an abundant number, since it is smaller than the sum of its proper divisors (1633288320).

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

638945280 is a wasteful number, since it uses less digits than its factorization.

638945280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2347 (or 2321 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 45.

The square root of 638945280 is about 25277.3669514845. The cubic root of 638945280 is about 861.3002146035.

The spelling of 638945280 in words is "six hundred thirty-eight million, nine hundred forty-five thousand, two hundred eighty".