Factorial/Examples/20

Example of Factorial

$20! = 2 \, 432 \, 902 \, 008 \, 176 \, 640 \, 000$

Prime Factors of $20!$

The prime decomposition of $20!$ is given as:

$20! = 2^{18} \times 3^8 \times 5^4 \times 7^2 \times 11 \times 13 \times 17 \times 19$

Proof

From $19$ Factorial:

$19! = 121 \, 645 \, 100 \, 408 \, 832 \, 000$

Then:

  121 645 100 408 832 000
x                      20
------------------------
2 432 902 008 176 640 000

$\blacksquare$

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $24$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $24$