78 (number)
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78 is a natural number that belongs to the sequence of standard whole numbers. It follows 77 and precedes 79. In base ten notation, it consists of two digits: 7 in the tens place and 8 in the units place.
78 is an even number, because it is divisible by 2 with no remainder. It is a composite number, meaning it has divisors other than 1 and itself.
Mathematical properties
The divisors of 78 are 1, 2, 3, 6, 13, 26, 39, and 78. Its prime factorization is 2 × 3 × 13. Consequently, 78 is squarefree, meaning each prime factor appears exactly once.
78 is a triangular number: it is the sum of the integers from 1 to 12 (1+2+3+...+12 = 78). It also equals the number of ways to choose 2 items from 13 distinct items, which is C(13,2) = 78.
Notation and representation
In Roman numerals, 78 is written LXXVIII. In binary, it is 1001110. In hexadecimal, it is 4E.
General use
78 appears in various numbering systems, such as telephone area codes, scientific classifications, and inventory lists. Such usage is labeling and does not reflect mathematical properties.