Sixty is the number after fifty-nine and before sixty-one. It is a round number and it is often used to represent an approximate value. In mathematics, 60 is a composite number, with factors of 1, 2, 3, 4, 5 and 6. It is also the sum of three consecutive prime numbers (13 + 17 + 19). In science, 60 or its multiples are often used as units for various measurements such as time (60 seconds in a minute), angles (60 degrees in a circle) or energy (1 calorie = 4.184 joules = 4184/60 kilojoules). In some cultures, sixty has special meanings associated with it such as the sixtieth birthday being celebrated as a milestone birthday.
