645996996 has 18 divisors (see below), whose sum is σ = 1632936942. Its totient is φ = 215332320.

The previous prime is 645996973. The next prime is 645997007. The reversal of 645996996 is 699699546.

645996996 is a `hidden beast` number, since 6 + 459 + 96 + 9 + 96 = 666.

It can be written as a sum of positive squares in only one way, i.e., 640798596 + 5198400 = 25314^2 + 2280^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8972145 + ... + 8972216.

It is an arithmetic number, because the mean of its divisors is an integer number (90718719).

Almost surely, 2^645996996 is an apocalyptic number.

It is an amenable number.

645996996 is an abundant number, since it is smaller than the sum of its proper divisors (986939946).

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

645996996 is a wasteful number, since it uses less digits than its factorization.

645996996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17944371 (or 17944366 counting only the distinct ones).

The product of its digits is 28343520, while the sum is 63.

The square root of 645996996 is about 25416.4709588094. The cubic root of 645996996 is about 864.4572072174.

The spelling of 645996996 in words is "six hundred forty-five million, nine hundred ninety-six thousand, nine hundred ninety-six".