645515609 has 2 divisors, whose sum is σ = 645515610. Its totient is φ = 645515608.

The previous prime is 645515597. The next prime is 645515617. The reversal of 645515609 is 906515546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 448253584 + 197262025 = 21172^2 + 14045^2 .

It is a cyclic number.

It is not a de Polignac number, because 645515609 - 2¹⁶ = 645450073 is a prime.

It is a super-3 number, since 3×645515609³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (645515639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322757804 + 322757805.

It is an arithmetic number, because the mean of its divisors is an integer number (322757805).

Almost surely, 2^645515609 is an apocalyptic number.

It is an amenable number.

645515609 is a deficient number, since it is larger than the sum of its proper divisors (1).

645515609 is an equidigital number, since it uses as much as digits as its factorization.

645515609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162000, while the sum is 41.

The square root of 645515609 is about 25406.9992128154. Note that the first 3 decimals coincide. The cubic root of 645515609 is about 864.2424271314.

The spelling of 645515609 in words is "six hundred forty-five million, five hundred fifteen thousand, six hundred nine".