645335440 has 80 divisors (see below), whose sum is σ = 1527692400. Its totient is φ = 253485056.

The previous prime is 645335407. The next prime is 645335441. The reversal of 645335440 is 44533546.

It can be written as a sum of positive squares in 8 ways, for example, as 167650704 + 477684736 = 12948^2 + 21856^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 645335396 and 645335405.

It is not an unprimeable number, because it can be changed into a prime (645335441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1658766 + ... + 1659154.

It is an arithmetic number, because the mean of its divisors is an integer number (19096155).

Almost surely, 2^645335440 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 645335440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (763846200).

645335440 is an abundant number, since it is smaller than the sum of its proper divisors (882356960).

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

645335440 is a wasteful number, since it uses less digits than its factorization.

645335440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 724 (or 718 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 34.

The square root of 645335440 is about 25403.4533085563. The cubic root of 645335440 is about 864.1620137995.

Adding to 645335440 its reverse (44533546), we get a palindrome (689868986).

The spelling of 645335440 in words is "six hundred forty-five million, three hundred thirty-five thousand, four hundred forty".