644450020 has 24 divisors (see below), whose sum is σ = 1355869368. Its totient is φ = 257299200.

The previous prime is 644450011. The next prime is 644450021. The reversal of 644450020 is 20054446.

It can be written as a sum of positive squares in 4 ways, for example, as 231222436 + 413227584 = 15206^2 + 20328^2 .

It is not an unprimeable number, because it can be changed into a prime (644450021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18961 + ... + 40600.

It is an arithmetic number, because the mean of its divisors is an integer number (56494557).

Almost surely, 2^644450020 is an apocalyptic number.

It is an amenable number.

644450020 is an abundant number, since it is smaller than the sum of its proper divisors (711419348).

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

644450020 is a wasteful number, since it uses less digits than its factorization.

644450020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60111 (or 60109 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 25.

The square root of 644450020 is about 25386.0201685889. The cubic root of 644450020 is about 863.7666139890.

The spelling of 644450020 in words is "six hundred forty-four million, four hundred fifty thousand, twenty".