87 (number)
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87 is a natural number that comes between 86 and 88. In the decimal number system it is written with two digits: 8 and 7, representing three tens and seven.
87 is not a prime number, as it factors into 3 × 29. Its divisors are therefore 1, 3, 29, and 87. Because it has three prime divisors and is divisible by more than one and itself, it is counted as a composite number.
Mathematical properties
The sum of the digits of 87 is 8 + 7 = 15, which is divisible by three; this is evidence that 87 is divisible by three. 87 is an odd number because it is not divisible by two. The sum of its proper divisors—1 + 3 + 29—is 33, which is less than 87, so it is a deficient number.
In other bases: 87 is written as 1010111 in binary, 127 in octal, and 57 in hexadecimal. In the Roman numeral system it is LXXXVII.
General use
Like other small numbers, 87 serves as a cardinal and ordinal number (eighty-seventh). It also appears in conventional systems such as sports uniforms, road route numbers, and year numbering; the meaning of such uses depends on the system employed and is not a mathematical property.