Designing light blinkers using 555 timer ic
You don't say what the LED voltage is, or (more importantly) the LED current, but definitely you cannot drive 170 LEDs directly. 

So you will need something like a single N-channel MOSFET to drive the LEDs. If each LED is 10mA and they are all in parallel, then you need to drive 1.7A. The 555 can drive the MOSFET gate directly, preferably with a small resistor in series. Make sure the MOSFET type (gate drive) is suitable for the 555 output voltage, especially if it is much less than 10V. 

Suppose that your supply is 5V and your LED Vf is 1.8V, you could connect them in pairs with 140 ohms per LED pair. (5-2*1.8)/0.01A = 140. Then the current would be only 0.85A (half the total current draw). With higher supply voltage it would be possible to put more LEDs in each small series chain. 

Concept: 







simulate this circuit &ndash; Schematic created using CircuitLab

There are a lot of MOSFET and LED questions on this site. Please give this a try and hopefully you can figure it out.