644899500 has 288 divisors, whose sum is σ = 2371299840. Its totient is φ = 144489600.

The previous prime is 644899487. The next prime is 644899517. The reversal of 644899500 is 5998446.

It is a happy number.

644899500 is a `hidden beast` number, since 64 + 4 + 89 + 9 + 500 = 666.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

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

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 95 ways as a sum of consecutive naturals, for example, 1858327 + ... + 1858673.

It is an arithmetic number, because the mean of its divisors is an integer number (8233680).

Almost surely, 2^644899500 is an apocalyptic number.

644899500 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 644899500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1185649920).

644899500 is an abundant number, since it is smaller than the sum of its proper divisors (1726400340).

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

644899500 is a wasteful number, since it uses less digits than its factorization.

644899500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438 (or 423 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 644899500 is about 25394.8715295037. The cubic root of 644899500 is about 863.9673823849.

The spelling of 644899500 in words is "six hundred forty-four million, eight hundred ninety-nine thousand, five hundred".