To determine the next number after 54 in the last row, it appears that the sequence could follow a pattern. Let me analyze the given numbers in the last row:

• The last row is: 21, 05, 34, 54.

If this sequence follows a mathematical pattern (e.g., addition, subtraction, multiplication, or another rule), I need to identify it. Let me calculate the differences between the terms:

1. $05 - 21 = -16$
2. $34 - 05 = 29$
3. $54 - 34 = 20$

The differences are irregular (-16, +29, +20), suggesting the sequence might not be arithmetic. It could follow another type of logic. Please confirm if there is additional context or a specific rule you're applying to this series. Alternatively, I can suggest further possibilities if more information is given.