Exact answers for huge numbers
Ordinary calculators and spreadsheets switch to approximate floating-point numbers after about 15 digits. A big number calculator keeps every digit, so you can add, subtract, multiply, divide, raise to powers, take remainders, find the GCF and compute factorials of enormous integers exactly.
This matters in number theory, cryptography, puzzles and checking large factorials or powers where every digit counts.
How it is calculated
Worked example
25 factorial
- 25!
- 15511210043330985984000000
- Number of digits
- 26
How big is big?
Numbers grow astonishingly fast. Factorials and powers reach hundreds of digits after only a few steps, which is exactly where ordinary calculators stop being exact.
| Value | Digits |
|---|---|
| 2^64 | 20 |
| 20! | 19 |
| 100! | 158 |
| 2^1000 | 302 |
Results with more than 24 digits are summarised on top, and the full exact number is shown below for you to copy.
Why normal calculators break here
A standard calculator or spreadsheet stores numbers in 64-bit floating point, which holds about 15–17 significant digits before it starts rounding. 25! (about 1.55 × 10²⁵) already has 26 digits — past that point, floating point gives a close but wrong-in-the-details answer. This calculator uses exact integer arithmetic instead, so every digit is correct.