645989816 has 32 divisors (see below), whose sum is σ = 1286928000. Its totient is φ = 303127776.

The previous prime is 645989791. The next prime is 645989831. The reversal of 645989816 is 618989546.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3596 + ... + 36123.

It is an arithmetic number, because the mean of its divisors is an integer number (40216500).

Almost surely, 2^645989816 is an apocalyptic number.

It is an amenable number.

645989816 is a deficient number, since it is larger than the sum of its proper divisors (640938184).

645989816 is a wasteful number, since it uses less digits than its factorization.

645989816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39851 (or 39847 counting only the distinct ones).

The product of its digits is 3732480, while the sum is 56.

The square root of 645989816 is about 25416.3297114277. The cubic root of 645989816 is about 864.4540045060.

The spelling of 645989816 in words is "six hundred forty-five million, nine hundred eighty-nine thousand, eight hundred sixteen".