644218376 has 8 divisors (see below), whose sum is σ = 1207909470. Its totient is φ = 322109184.

The previous prime is 644218373. The next prime is 644218391. The reversal of 644218376 is 673812446.

644218376 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 618715876 + 25502500 = 24874^2 + 5050^2 .

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 (644218373) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40263641 + ... + 40263656.

Almost surely, 2^644218376 is an apocalyptic number.

It is an amenable number.

644218376 is a deficient number, since it is larger than the sum of its proper divisors (563691094).

644218376 is a wasteful number, since it uses less digits than its factorization.

644218376 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80527303 (or 80527299 counting only the distinct ones).

The product of its digits is 193536, while the sum is 41.

The square root of 644218376 is about 25381.4573261663. The cubic root of 644218376 is about 863.6631095405.

The spelling of 644218376 in words is "six hundred forty-four million, two hundred eighteen thousand, three hundred seventy-six".