53

This number is a prime.

Just showing those entries submitted by 'Merickel': (Click here to show all)

This number is an emirp in 11 straight bases, from base 30 through base 40. Does any other number have such a string of bases attached to it? [Merickel]

Doubling 53 places a 0 between the digits of its index, i.e., 2*(5+3). [Merickel]