A more modest version of 10^10^18

 : hypercalc

Hypercalc is distributed under the terms and conditions of the
GNU General Public License, version 2, June 1991. Type 'help gpl'
at the Hypercalc prompt for details.

       Hypercalc by Robert Munafo, 2014 Apr 22
      Go ahead -- just TRY to make me overflow!
           _ _
           |_| . . ._   _  ._  _ ._  |  _
           | | | | | ) (-` |  (  ,-| | (
           ~ ~  7  |~   ~' ~   ~ `~` ~  ~
               -'   mrob.com/hypercalc

     Enter expressions, or type 'help' for help.


C1 = day = 24

R1 = day: 24

C2 = year = 365.25 * day

R2 = year: 8766

C3 = lifetime = 75 * year

R3 = lifetime: 657450

C4 = lifetime_bits = lifetime * 12

R4 = lifetime_bits: 7889400

C5 = possible_lifetimes = 2^lifetime_bits

R5 = possible_lifetimes: 1.116326 x 10 ^ 2374946

C6 =