645138320 has 40 divisors (see below), whose sum is σ = 1511421120. Its totient is φ = 256081280.

The previous prime is 645138317. The next prime is 645138323. The reversal of 645138320 is 23831546.

645138320 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (645138317) and next prime (645138323).

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (645138323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20300 + ... + 41259.

It is an arithmetic number, because the mean of its divisors is an integer number (37785528).

Almost surely, 2^645138320 is an apocalyptic number.

It is an amenable number.

645138320 is an abundant number, since it is smaller than the sum of its proper divisors (866282800).

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

645138320 is a wasteful number, since it uses less digits than its factorization.

645138320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61703 (or 61697 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 32.

The square root of 645138320 is about 25399.5732247611. The cubic root of 645138320 is about 864.0740177215.

Adding to 645138320 its reverse (23831546), we get a palindrome (668969866).

The spelling of 645138320 in words is "six hundred forty-five million, one hundred thirty-eight thousand, three hundred twenty".