Back to [Numbers 1200-1299]

1,231

[Math.]  A digit-wraparound prime number.

 

1231, 12371249

[Math.]  A sequence of consecutive reversible prime numbers:  1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249 and 1259.

 

1,233

[Math.]  1233 = 122+332 and 8833 = 882+332, where 12+88 = 100.

 

1,234

[Math.]

1×8+1 = 9

12×8+2 = 98

123×8+3 = 987

1,234×8+4 = 9,876

12,345×8+5 = 98,765

123,456×8+6 = 987,654

1,234,567×8+7 = 9,876,543

12,345,678×8+8 = 98,765,432

123,456,789×8+9 = 987,654,321

1,234,567,890×8+90 = 9,876,543,210

      (start of a new cycle)

12,345,678,901×8+901 = 98,765,432,109

123,456,789,012×8+9,002 = 987,654,321,098

1,234,567,890,123×8+90,003 = 9,876,543,210,987

12,345,678,901,234×8+900,004 = 98,765,432,109,876

123,456,789,012,345×8+9,000,005 = 987,654,321,098,765

1,234,567,890,123,456×8+90,000,006 = 9,876,543,210,987,654

12,345,678,901,234,567×8+900,000,007 = 98,765,432,109,876,543

123,456,789,012,345,678×8+9,000,000,008 = 987,654,321,098,765,432

1,234,567,890,123,456,789×8+90000000009 = 9,876,543,210,987,654,321

12,345,678,901,234,567,890×8+ 900000000090 = 98,765,432,109,876,543,210

... (end of cycle) ...

 

[Math.] 

1×9+2 = 11          

12×9+3 = 111      

123×9+4 = 1,111

1234×9+5 = 11,111

12,345×9+6 = 111,111

123,456×9+7 = 1,111,111

1,234,567×9+8 = 11,111,111

12,345,678×9+9 = 111,111,111 

123,456,789×9+10 = 1,111,111,111

1,234,567,900×9+11 = 11,111,111,111

...

 

1,240

[Math.]  A pyramidal number (sum of all squares of integers from 1 to 15): 1240 = 12+22+…+142+152.

 

1,244

[Geology]  The length (feet) of the 726-foot-high Hoover Dam, on the Colorado River, built in 1931-1936 and cost U.S. $385 million. It is home to Lake Mead, the U.S. largest reservoir.

 

1,249

[Math.]  Its odd powers end with 1249. Its even powers end with 0001.

 

1,210-1229 (separate page

           

1,230-1249 (separate page)

 

1,250-1279 (separate page)

           

1,280-1299 (separate page)