660 = 22 × 3 × 5 × 11 Sum of four consecutive primes (157 + 163 + 167 + 173) Sum of six consecutive primes (101 + 103 + 107 + 109 + 113 + 127) Sum of eight consecutive primes (67 + 71 + 73 + 79 + 83 + 89 + 97 + 101) Sparsely totient number