7,810

[Math.]  Square numbers, which are concatenation of 2 consecutive numbers: 78102 = 60,996,100; 90792 = 82,428,241 and 99012 = 98,029,801.

7,818

[Library]  ISBN-0-7818 is the International Standard Book Number for books published by Hippocrene Books.

7,820

[Geology]  The length (km, 4860 miles) of the longest highway in the world: Trans-Canada highway, from Vancouver Island to St. John’s, Newfoundland.

7,821

[Math.]  Two multiples of number 7884, 7821×2 = 15,642 and 7821×9 = 70,389, use each of 10 digits 0-9 once.

7,824

[Math.]  7824 = 211+37+55+73+112.

[Math.]  Two multiples of number 7884, 7824×5 = 39,120 and 7824×7 = 54,768, use each of 10 digits 0-9 once.

7,842

[Math.]  7842 = 65+43+21.

7,851

[Math.]  7851 = 7777+8+55+11.

7,852

[Math.]  7852 = 4×1963, using each of 9 digits 1-9 once.

7,856

[Math.]  7856 = 7777+8+5+66.

7,863

[Library]  ISBN-0-7863 is the International Standard Book Number for books published by Irwin Professional Publishing.

7,868

[Library]  ISBN-0-7868 is the International Standard Book Number for books published by Hyperion/Madison Press Book.

7,875

[Math.]  A triangular number (sum of all integers from 1 to 125): 7875 = 1+2+…+124+125.

7,879

[Math.]  A sequence of prime numbers: 5857, 6869, 7879 and 8887, each formed by 2 consecutive numbers, and their differences are 1012, 1010 and 1008, which are three consecutive even numbers.

7,884

[Math.]  Two multiples of number 7884, 7884×2 = 15,768 and 7884×5 = 39,420, use each of 10 digits 0-9 once.

7,894

[Math.]  The ratio 63152/7894 = 8, using each of 9 digits 1-9 once, shows how to arrange a 9-book set on 2 shelves to mark the book #8.

[Library]  ISBN-0-7894 is the International Standard Book Number for books published by Dorling Kindersley Publishing, (Covent Garden Books).