638721228800 has 144 divisors (see below), whose sum is σ = 1585800398205. Its totient is φ = 255199150080.

The previous prime is 638721228793. The next prime is 638721228809. The reversal of 638721228800 is 8822127836.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 625946804224 + 12774424576 = 791168^2 + 113024^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=565120.

It is not an unprimeable number, because it can be changed into a prime (638721228809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 723353159 + ... + 723354041.

Almost surely, 2^638721228800 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 638721228800

638721228800 is an abundant number, since it is smaller than the sum of its proper divisors (947079169405).

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

638721228800 is an frugal number, since it uses more digits than its factorization.

638721228800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1806 (or 890 counting only the distinct ones).

The product of its (nonzero) digits is 516096, while the sum is 47.

The spelling of 638721228800 in words is "six hundred thirty-eight billion, seven hundred twenty-one million, two hundred twenty-eight thousand, eight hundred".