In roman number system ,fifteen symbols are needed to express 999

81 is the square of the sum of its digits

50 is the smallest number that can be written as the sum of 2 square in 2 ways

25 is the smallest square that can be written as a sum of 2 squares

Counting is nearly as old as speech and numerals are as old as writing

Numbers were invented before writing was. So, initially there were no written symbols for numbers

The concept of zero is credited to the Indian astronomer Brahmagupta ? ? ?

The earliest chinese number system used a number of symbols to represent numbers and was based on the decimal system. The system was additive, and not positional, so there was no need for a zero. A number 2437 would be represented by the symbol for 2000, followed by that for 400, that for 30 and then by that for 400, that for 30 and then by the symbol for 7.

153 is a very special number because 153 = 1^{3} + 5^{3} + 3^{3}. Such numbers are called Armstrong numbers. Some other Armstrong numbers are 370, 371, 407. 153 is also equal to 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17.