4973

This number is a prime.

The 666th prime. If you were to intersperse the digits of 666 into this number (i.e., 4696763), then another prime would be formed. [Patterson]

Add this prime number to its index (666) for yet another prime number. [Eberhardt]

If you place the number of primes less than or equal to 4973 between any adjacent digits of 4973, then another three primes are formed, i.e., 4666973, 4966673 and 4976663. [Lewicki]