664994816 has 44 divisors (see below), whose sum is σ = 1354532652. Its totient is φ = 326197248.

The previous prime is 664994801. The next prime is 664994819. The reversal of 664994816 is 618499466.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 403849216 + 261145600 = 20096^2 + 16160^2 .

It is a Harshad number since it is a multiple of its sum of digits (53).

It is not an unprimeable number, because it can be changed into a prime (664994819) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48146 + ... + 60398.

It is an arithmetic number, because the mean of its divisors is an integer number (30784833).

Almost surely, 2^664994816 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 664994816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (677266326).

664994816 is an abundant number, since it is smaller than the sum of its proper divisors (689537836).

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

664994816 is a wasteful number, since it uses less digits than its factorization.

664994816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12326 (or 12308 counting only the distinct ones).

The product of its digits is 2239488, while the sum is 53.

The square root of 664994816 is about 25787.4934028106. The cubic root of 664994816 is about 872.8496054104.

The spelling of 664994816 in words is "six hundred sixty-four million, nine hundred ninety-four thousand, eight hundred sixteen".