645568997 has 4 divisors (see below), whose sum is σ = 645758880. Its totient is φ = 645379116.

The previous prime is 645568993. The next prime is 645569009. The reversal of 645568997 is 799865546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 799865546 = 2 ⋅399932773.

It is a cyclic number.

It is not a de Polignac number, because 645568997 - 2² = 645568993 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645568993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 89747 + ... + 96672.

It is an arithmetic number, because the mean of its divisors is an integer number (161439720).

Almost surely, 2^645568997 is an apocalyptic number.

It is an amenable number.

645568997 is a deficient number, since it is larger than the sum of its proper divisors (189883).

645568997 is a wasteful number, since it uses less digits than its factorization.

645568997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189882.

The product of its digits is 16329600, while the sum is 59.

The square root of 645568997 is about 25408.0498464561. The cubic root of 645568997 is about 864.2662524797.

The spelling of 645568997 in words is "six hundred forty-five million, five hundred sixty-eight thousand, nine hundred ninety-seven".