644470544 has 40 divisors (see below), whose sum is σ = 1327917240. Its totient is φ = 301948928.

The previous prime is 644470543. The next prime is 644470549. The reversal of 644470544 is 445074446.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 232867600 + 411602944 = 15260^2 + 20288^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644470498 and 644470507.

It is not an unprimeable number, because it can be changed into a prime (644470543) 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, 58292 + ... + 68460.

It is an arithmetic number, because the mean of its divisors is an integer number (33197931).

Almost surely, 2^644470544 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644470544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (663958620).

644470544 is an abundant number, since it is smaller than the sum of its proper divisors (683446696).

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

644470544 is a wasteful number, since it uses less digits than its factorization.

644470544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10427 (or 10421 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 38.

The square root of 644470544 is about 25386.4244036060. The cubic root of 644470544 is about 863.7757834396.

The spelling of 644470544 in words is "six hundred forty-four million, four hundred seventy thousand, five hundred forty-four".