644195160 has 512 divisors, whose sum is σ = 2626560000. Its totient is φ = 140216832.

The previous prime is 644195147. The next prime is 644195173. The reversal of 644195160 is 61591446.

644195160 is a `hidden beast` number, since 644 + 1 + 9 + 5 + 1 + 6 + 0 = 666.

It is a Cunningham number, because it is equal to 25381²-1.

It is an interprime number because it is at equal distance from previous prime (644195147) and next prime (644195173).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 13706257 + ... + 13706303.

It is an arithmetic number, because the mean of its divisors is an integer number (5130000).

Almost surely, 2^644195160 is an apocalyptic number.

644195160 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 644195160, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1313280000).

644195160 is an abundant number, since it is smaller than the sum of its proper divisors (1982364840).

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

644195160 is a wasteful number, since it uses less digits than its factorization.

644195160 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 644195160 is about 25380.9999803002. Note that the first 4 decimals coincide. The cubic root of 644195160 is about 863.6527346716.

The spelling of 644195160 in words is "six hundred forty-four million, one hundred ninety-five thousand, one hundred sixty".