They are infinite, beginning with these: 231, 462, 693, 924, 1155 . . .
21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, . . .
21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231 . . .
21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, 273, . . .
Multiply 21 and 11 to get a common multiple. Since 21 and 11 have no common factors, that also happens to be the least common multiple.All other common multiples are multiples of this least common multiple.
21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, . . .
77, 154, 231, 308 are multiples of 77
The LCM is 231.
The LCM of 11 and 21 is 231
93,186,279,372 and so on
231
21 x 11 = 231 21 x11 ---- 21 +210 ---- 231