644081364 has 72 divisors (see below), whose sum is σ = 1652047488. Its totient is φ = 211559040.

The previous prime is 644081357. The next prime is 644081369. The reversal of 644081364 is 463180446.

644081364 is a `hidden beast` number, since 644 + 0 + 8 + 1 + 3 + 6 + 4 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644081369) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1043584 + ... + 1044200.

It is an arithmetic number, because the mean of its divisors is an integer number (22945104).

Almost surely, 2^644081364 is an apocalyptic number.

It is an amenable number.

644081364 is an abundant number, since it is smaller than the sum of its proper divisors (1007966124).

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

644081364 is a wasteful number, since it uses less digits than its factorization.

644081364 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1005 (or 1000 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 36.

The square root of 644081364 is about 25378.7581256452. The cubic root of 644081364 is about 863.6018774054.

The spelling of 644081364 in words is "six hundred forty-four million, eighty-one thousand, three hundred sixty-four".