5. A book has 2020 pages. If a page number can form 2 or more (including 2) consecutive natural numbers, we call this page a "consecutive page." For example: "21", "213", "1324", "9789", "109" are page numbers formed by "2, 1", "1, 2, 3", "1, 2, 3, 4", "97, 98", "9, 10" respectively, so "21", "213", "1324", "9789", "109" are consecutive pages, but "22", "217", "122" are not consecutive pages. How many consecutive pages are there in this book?
【Answer】188
【Analysis】Case analysis
2 consecutive page numbers:
Descending: $10,21,32, \cdots \cdots, 87,98$, a total of 9
Ascending: 12, 23, 34, $\cdots \cdots, 89$, a total of 8
3 consecutive page numbers:
Containing 10: $9^{\sim} 10$ consecutive, $109,190,901,910$, a total of 4
Containing $0: 0,1,2$ consecutive, same as above, a total of 4
Not containing 0: 3 consecutive non-zero natural numbers $123, \ldots 789$, $7 \times(3 \times 2 \times 1)=42$ 
4 consecutive page numbers:
(1): $8,9,10$ consecutive, 6
(2): $0,1,2,3 \quad 7$
(3): $1,2,3,4 \quad 6$
(4): 10,11, or 11,12 6
(5) “ 12, 13" “ 18,19 ” $7 \times 6=42$
(6) “ 19,20 ”, $1920,1290,1209,1902,1029,1092$, a total of $6+1=7$
(7) “ 20, 21” , 2012, 122, 1202, 1220, a total of 4
(8) “ 30,31 ” “ 90,91 ”, $3 \times 7=21$
(9) “ 21,22 ” 1
(10) "31, 32" “91, 92", $3 \times 7=21$
$$
9+8+4+4+42+6+7+6+6+42+7+4+21+1+21=188 \text {  }
$$