645632209 has 2 divisors, whose sum is σ = 645632210. Its totient is φ = 645632208.

The previous prime is 645632177. The next prime is 645632227. The reversal of 645632209 is 902236546.

645632209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 427331584 + 218300625 = 20672^2 + 14775^2 .

It is a cyclic number.

It is not a de Polignac number, because 645632209 - 2⁵ = 645632177 is a prime.

It is equal to p_33578047 and since 645632209 and 33578047 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (645632809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322816104 + 322816105.

It is an arithmetic number, because the mean of its divisors is an integer number (322816105).

Almost surely, 2^645632209 is an apocalyptic number.

It is an amenable number.

645632209 is a deficient number, since it is larger than the sum of its proper divisors (1).

645632209 is an equidigital number, since it uses as much as digits as its factorization.

645632209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 77760, while the sum is 37.

The square root of 645632209 is about 25409.2937524836. The cubic root of 645632209 is about 864.2944602652.

The spelling of 645632209 in words is "six hundred forty-five million, six hundred thirty-two thousand, two hundred nine".