Divisibility

1 we express a number as a linear combination of powers of 102 for example1980=1*10^3+9*10^2+8*10^1+0*10^0we get [1 9 8 1]apply divisibility rule by 7remaining digits-2(last digit)k=11 9 8 -2(1)=196k=219 - 2(6)=7k=30-2(7)=-14 which is divisible by 7stop we get a negative number Platforms: Matlab

Enter a whole number from 1 to 150. The Number Dictionary tells you divisibility as well as many other things! Is there a prime number that is ALSO triangular? Is there a number that is BOTH a cube and a square? Platforms: Mac

Math::Numbers is a Perl module that contains methods for mathematical approaches of concepts of the number theory. SYNOPSIS use Math::Numbers; my $a = 123; my $b = 34; my $numbers = Math::Numbers->new($a, $b [, ...]); print "They are coprimes (relatively primes)!n" if... Platforms: *nix