644783144 has 8 divisors (see below), whose sum is σ = 1208968410. Its totient is φ = 322391568.

The previous prime is 644783131. The next prime is 644783147. The reversal of 644783144 is 441387446.

It can be written as a sum of positive squares in only one way, i.e., 644652100 + 131044 = 25390^2 + 362^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (644783147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40298939 + ... + 40298954.

Almost surely, 2^644783144 is an apocalyptic number.

It is an amenable number.

644783144 is a deficient number, since it is larger than the sum of its proper divisors (564185266).

644783144 is a wasteful number, since it uses less digits than its factorization.

644783144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80597899 (or 80597895 counting only the distinct ones).

The product of its digits is 258048, while the sum is 41.

The square root of 644783144 is about 25392.5804911592. The cubic root of 644783144 is about 863.9154188178.

The spelling of 644783144 in words is "six hundred forty-four million, seven hundred eighty-three thousand, one hundred forty-four".