945 is the first odd abundant number, discovered by Claude-Gaspar Bachet (1581-1638): 945 = 33 x 5 x 7 and its divisors sum to 975; 975 is greater than 945, so 945 is an abundant number. Odd abundant number are rare; only 23 occur below 10,000.
945 is the smallest odd primitive semiperfect number. A semiperfect number is equal to the sum of all or some of its proper divisors. A semiperfect number that is not divisible by any smaller semiperfect number is a primitive semiperfect number.
945 is 1661 in base 8.
NGC 945 is a galaxy in the constellation Cetus.
Source: Wolfram MathWorld
