645143209 has 2 divisors, whose sum is σ = 645143210. Its totient is φ = 645143208.

The previous prime is 645143179. The next prime is 645143227. The reversal of 645143209 is 902341546.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 519703209 + 125440000 = 22797^2 + 11200^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645143209 is a prime.

It is not a weakly prime, because it can be changed into another prime (645143299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322571604 + 322571605.

It is an arithmetic number, because the mean of its divisors is an integer number (322571605).

Almost surely, 2^645143209 is an apocalyptic number.

It is an amenable number.

645143209 is a deficient number, since it is larger than the sum of its proper divisors (1).

645143209 is an equidigital number, since it uses as much as digits as its factorization.

645143209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 34.

The square root of 645143209 is about 25399.6694663533. The cubic root of 645143209 is about 864.0762004302.

The spelling of 645143209 in words is "six hundred forty-five million, one hundred forty-three thousand, two hundred nine".