645543517 has 2 divisors, whose sum is σ = 645543518. Its totient is φ = 645543516.

The previous prime is 645543511. The next prime is 645543581. The reversal of 645543517 is 715345546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 607671801 + 37871716 = 24651^2 + 6154^2 .

It is a cyclic number.

It is not a de Polignac number, because 645543517 - 2²³ = 637154909 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 645543517.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645543511) 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 as a sum of consecutive naturals, namely, 322771758 + 322771759.

It is an arithmetic number, because the mean of its divisors is an integer number (322771759).

Almost surely, 2^645543517 is an apocalyptic number.

It is an amenable number.

645543517 is a deficient number, since it is larger than the sum of its proper divisors (1).

645543517 is an equidigital number, since it uses as much as digits as its factorization.

645543517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 252000, while the sum is 40.

The square root of 645543517 is about 25407.5484256156. The cubic root of 645543517 is about 864.2548817386.

The spelling of 645543517 in words is "six hundred forty-five million, five hundred forty-three thousand, five hundred seventeen".