640021824 has 140 divisors (see below), whose sum is σ = 2043380724. Its totient is φ = 196909056.

The previous prime is 640021813. The next prime is 640021861. The reversal of 640021824 is 428120046.

640021824 is a `hidden beast` number, since 640 + 0 + 2 + 18 + 2 + 4 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 58247424 + 581774400 = 7632^2 + 24120^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 62644 + ... + 72140.

Almost surely, 2^640021824 is an apocalyptic number.

640021824 is a gapful number since it is divisible by the number (64) 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 640021824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1021690362).

640021824 is an abundant number, since it is smaller than the sum of its proper divisors (1403358900).

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

640021824 is a wasteful number, since it uses less digits than its factorization.

640021824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9534 (or 9515 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 640021824 is about 25298.6526123428. The cubic root of 640021824 is about 861.7836713978.

It can be divided in two parts, 6400 and 21824, that added together give a square (28224 = 168²).

The spelling of 640021824 in words is "six hundred forty million, twenty-one thousand, eight hundred twenty-four".