644696784 has 30 divisors (see below), whose sum is σ = 1804255986. Its totient is φ = 214898880.

The previous prime is 644696749. The next prime is 644696849. The reversal of 644696784 is 487696446.

It can be written as a sum of positive squares in only one way, i.e., 570254400 + 74442384 = 23880^2 + 8628^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 644696784.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2238387 + ... + 2238674.

Almost surely, 2^644696784 is an apocalyptic number.

It is an amenable number.

644696784 is an abundant number, since it is smaller than the sum of its proper divisors (1159559202).

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

644696784 is a wasteful number, since it uses less digits than its factorization.

644696784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4477075 (or 4477066 counting only the distinct ones).

The product of its digits is 6967296, while the sum is 54.

The square root of 644696784 is about 25390.8799374894. The cubic root of 644696784 is about 863.8768471588.

It can be divided in two parts, 64469 and 6784, that added together give a triangular number (71253 = T₃₇₇).

The spelling of 644696784 in words is "six hundred forty-four million, six hundred ninety-six thousand, seven hundred eighty-four".