yes, 81 is odd because the last number (1) in the the number is odd
here are most of the odd numbers:
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39.......
here is a list now of most even numbers:
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40......
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27 and 81 are the odd numbers. Since odd numbers are 1, 3, 5, 7 and 9, look at the last number and you will be able to tell if it's odd or even.
Odd
To find the sum of the first 81 odd numbers, we can use the formula for the sum of an arithmetic series: Sn = n/2 * (2a + (n-1)d), where n is the number of terms, a is the first term, and d is the common difference. In this case, n = 81, a = 1 (first odd number), and d = 2 (since the difference between consecutive odd numbers is 2). Plugging these values into the formula, we get: S81 = 81/2 * (2(1) + (81-1)2) = 81/2 * (2 + 160) = 81/2 * 162 = 6561. Therefore, the sum of the first 81 odd numbers is 6561.
The only number in that list which is not a square number is 27. 27 is a cube number.
3764. The rest are perfect squares.