645984978 has 16 divisors (see below), whose sum is σ = 1300200960. Its totient is φ = 213956496.

The previous prime is 645984949. The next prime is 645984979. The reversal of 645984978 is 879489546.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645984979) 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 7 ways as a sum of consecutive naturals, for example, 341938 + ... + 343821.

It is an arithmetic number, because the mean of its divisors is an integer number (81262560).

Almost surely, 2^645984978 is an apocalyptic number.

645984978 is an abundant number, since it is smaller than the sum of its proper divisors (654215982).

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

645984978 is a wasteful number, since it uses less digits than its factorization.

645984978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 685921.

The product of its digits is 17418240, while the sum is 60.

The square root of 645984978 is about 25416.2345362172. The cubic root of 645984978 is about 864.4518464540.

The spelling of 645984978 in words is "six hundred forty-five million, nine hundred eighty-four thousand, nine hundred seventy-eight".