What is the mean of all possible positive three-digit integers in which no digit is repeated and all digits are prime?

mean(235 , 237 , 253 , 257 , 273 , 275 , 325 , 327 , 352 , 357 , 372 , 375 , 523 , 527 , 532 , 537 , 572 , 573 , 723 , 725 , 732 , 735 , 752 , 753)==471.75 == 11,322 / 24 ==471.75