Answer
Multiples of 642 are:
642, 1284, 1926, 2568, 3210, 3852, 4494, 5136, 5778, 6420, 7062, 7704, 8346, 8988, 9630, 10272, 10914, 11556, 12198, 12840, 13482, 14124, 14766, 15408, 16050, 16692, 17334, 17976, 18618, 19260, 19902, 20544, 21186, 21828, 22470, 23112, 23754, 24396, 25038, 25680, 26322, 26964, 27606, 28248, 28890, 29532, 30174, 30816, 31458
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