6011

6011 is a prime number. Rotating 6011 by 180 degrees (turning it upside down) produces 1109, another prime.

6011 is a member of the Fibonacci-like sequence starting with 3 and 8.

6011 is a prime p such that the product its digits (excluding 0) is a divisor of p + 1.

6011² uses only the digits 1, 2, 3, and 6: 36132121.

60/11 equals 5.4545. . . , the exact time difference between consecutive overlaps of the hour and minute hands, which occurs 11 times every 60 minutes.

6011 is the postal code for Peppermint Grove, Western Australia, a suburb of Perth.

Source: Prime Curios!