644508771822 has 96 divisors (see below), whose sum is σ = 1496862581760. Its totient is φ = 199923123840.

The previous prime is 644508771793. The next prime is 644508771839. The reversal of 644508771822 is 228177805446.

644508771822 is a `hidden beast` number, since 6 + 4 + 450 + 8 + 7 + 7 + 182 + 2 = 666.

It is a super-2 number, since 2×644508771822² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 6040783 + ... + 6146549.

It is an arithmetic number, because the mean of its divisors is an integer number (15592318560).

Almost surely, 2^644508771822 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644508771822, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (748431290880).

644508771822 is an abundant number, since it is smaller than the sum of its proper divisors (852353809938).

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

644508771822 is a wasteful number, since it uses less digits than its factorization.

644508771822 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106198 (or 106195 counting only the distinct ones).

The product of its (nonzero) digits is 6021120, while the sum is 54.

The spelling of 644508771822 in words is "six hundred forty-four billion, five hundred eight million, seven hundred seventy-one thousand, eight hundred twenty-two".