This is a two part question, so I'll answer it in two parts.
1. In order to set a value to this air rifle I need to know a few things. Is everything working and what shape is it in. Give it some sort of rating like Poor, Fair, Good, Very Good or Excellent condition. Without more information it is not possible to answer this part of the question.
2. There are several airgun cleaning kits on the marked (Crosman, RWS and Gamo) sell them. NEVER, under any circumstance, use firearm cleaning agents on an air rifle. The agents will destroy the seals. Never use regular oils on an air rifle. Use Crosman pellgun oil or RWS air gun oil. These are designed for airguns. You can purchase "Cleaning pellets from Pyramyd Air on the web along with all the airgun cleaning agents that you need.
See the link below for an example.
The 3 is in the units position, so it is worth 3.
521 years ago.
512.715 becomes 513
3x117=513 or 513/3=117 or 513/117=3
100-1000 USD
Yes, 513 is composite. The factors of 513 are: 1, 3, 9, 19, 27, 57, 171, 513.
6z-513 = -507
9*57=513
513 = 201
513, as a fraction, is 513/1 or 1026/2 etc.
513 is not prime. 513 = 3 * 3 * 3 * 19
513/2= 256.5