3 is a triangular number that is also prime.Here is a list of some of the first few triangular numbers:0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630, 666, 703, 741, 780, 820, 861, 903, 946, 990, 1035, 1081, 1128, 1176, 1225, 1275
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435,
The prime numbers from 21 to 40 are 23, 29, 31, and 37.
Out of those 100 numbers, 21 of them are prime numbers, so the remaining (100 - 21) = 79 are composite.
There are 3 prime numbers from 21 to 35:23, 29 and 31
The answer would be 15 and 21. The triangular numbers are 1,3,6,10,15,21,28,36,45,55,66,78. 15 plus 21 is 36 which is on the list. 21 minus 15 is 6 and that is on the list as well.
Yes, the number 21 is indeed a triangular number. Other triangular numbers are 6,10, and 15.
Triangular numbers follow the form (n^2+n)/2
Because it is ! The first 10 triangular numbers are... 1,3,6,10,15,21,28,36,45 & 55
Thre are infinitely many solutions. The smalest set with two different triangular number adding to another is 6 + 15 = 21
No. The first few triangular numbers are 1, 3, 6, 10, 15, 21, 28, ...
21, 28, 36, 45
The triangular numbers between 1 and 66 are: 3, 6, 10, 15, 21, 28, 36, 45 and 55.
32 is not a triangular number. The first few triangular numbers are 1, 3, 6, 10, 15, 21, 28, 36, 45, ...
The first twelve triangular numbers are: 1 3 6 10 15 21 28 36 45 55 66 78
1, 3, 6, 10, 15, 21
No, 23 is not a triangular number. Here are a few examples of triangular numbers: 21, 28, 55, 45, 78 and 91.