9533

This number is a prime.

9533 is just the sixth prime p for which p - ssd(p) = q^2, where q is prime and ssd(p) is the sum of the squared decimal digits of p. ssd(9533) = 81+25+9+9 = 124 and 9533-124 = 9409 = 97^2. The five smaller primes like this are 11, 2903, 3533, 3803, and 5197. [Keith]