641821800 has 96 divisors (see below), whose sum is σ = 1998622080. Its totient is φ = 170380800.

The previous prime is 641821783. The next prime is 641821811. The reversal of 641821800 is 8128146.

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

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 137505 + ... + 142095.

It is an arithmetic number, because the mean of its divisors is an integer number (20818980).

Almost surely, 2^641821800 is an apocalyptic number.

641821800 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 641821800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (999311040).

641821800 is an abundant number, since it is smaller than the sum of its proper divisors (1356800280).

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

641821800 is a wasteful number, since it uses less digits than its factorization.

641821800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4843 (or 4834 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 641821800 is about 25334.2021780833. The cubic root of 641821800 is about 862.5907990945.

Adding to 641821800 its reverse (8128146), we get a palindrome (649949946).

It can be divided in two parts, 64182 and 1800, that multiplied together give a triangular number (115527600 = T₁₅₂₀₀).

The spelling of 641821800 in words is "six hundred forty-one million, eight hundred twenty-one thousand, eight hundred".