644871000 has 128 divisors (see below), whose sum is σ = 2059200000. Its totient is φ = 167932800.

The previous prime is 644870969. The next prime is 644871011. The reversal of 644871000 is 178446.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 126501 + ... + 131499.

It is an arithmetic number, because the mean of its divisors is an integer number (16087500).

Almost surely, 2^644871000 is an apocalyptic number.

644871000 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 644871000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1029600000).

644871000 is an abundant number, since it is smaller than the sum of its proper divisors (1414329000).

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

644871000 is a wasteful number, since it uses less digits than its factorization.

644871000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5066 (or 5052 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 644871000 is about 25394.3103863838. The cubic root of 644871000 is about 863.9546551134.

The spelling of 644871000 in words is "six hundred forty-four million, eight hundred seventy-one thousand".