998 is the integer that follows 997 and precedes 999. It is an even, three-digit number notable for being two less than 1000 and for its simple arithmetic structure. In everyday contexts it appears as a numeric label, a year designation (AD 998 or 998 BC), and in codes such as telephone country and emergency numbers in some countries.
Mathematical characteristics
Arithmetically, 998 is a composite number with the prime factorization 2 × 499. Because it is the product of two primes (one of them 2), it is a semiprime. Its positive divisors are 1, 2, 499 and 998; the sum of proper divisors is 502, which is less than 998, so the number is classified as deficient. The Euler totient function φ(998) equals 498.
Representations and digital properties
In different numeral systems 998 is written as follows: binary 1111100110, octal 1746, and hexadecimal 3E6. Its decimal digit sum is 9+9+8 = 26, giving a digital root of 8. Because it ends in 8 it is divisible by 2 but not by 4; it is not divisible by 3 or 5.
Context, uses and examples
As a label, 998 can denote model numbers, addresses, product codes, or years. In telecommunications, +998 is the international dialing code for Uzbekistan. In some countries 998 is also used as a direct emergency number for firefighting services (for example, traditionally in Poland), although modern practice emphasizes universal emergency numbers as well.
Notable facts and distinctions
- 998 is the largest even three-digit number in base ten (the next even number, 1000, has four digits).
- Its Roman numeral representation is CMXCVIII (900 + 90 + 8).
- Because one factor is 2 and the other a large prime (499), many multiplicative functions take simple values here (for example, σ(998)=1500).
While 998 does not possess many special or exotic mathematical properties beyond being a simple semiprime, its proximity to 1000 and its roles in coding and numbering systems make it a frequent incidental reference in technical and everyday contexts.