An N-digit number X, such that the last N-digits of X² == X
e.g. 2-digit "25", 25² is "625".
const cn = require('curiousn').curiousn;
const ansArray = cn(2);
// there are always 2 curious numbers of length N, so you get an array
// because the curious numbers get big quick, we use "big-integer" // which means you need toString() to see the value
console.log( ansArray[0].toString() );
See