645733561 has 6 divisors (see below), whose sum is σ = 709773386. Its totient is φ = 587030400.

The previous prime is 645733553. The next prime is 645733567. The reversal of 645733561 is 165337546.

It can be written as a sum of positive squares in only one way, i.e., 637865536 + 7868025 = 25256^2 + 2805^2 .

It is not a de Polignac number, because 645733561 - 2³ = 645733553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645733567) 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 5 ways as a sum of consecutive naturals, for example, 2668200 + ... + 2668441.

Almost surely, 2^645733561 is an apocalyptic number.

It is an amenable number.

645733561 is a deficient number, since it is larger than the sum of its proper divisors (64039825).

645733561 is a wasteful number, since it uses less digits than its factorization.

645733561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5336663 (or 5336652 counting only the distinct ones).

The product of its digits is 226800, while the sum is 40.

The square root of 645733561 is about 25411.2880625914. The cubic root of 645733561 is about 864.3396838396.

The spelling of 645733561 in words is "six hundred forty-five million, seven hundred thirty-three thousand, five hundred sixty-one".