545

545 is a natural number that comes after 544 and before 546. It is odd and composite.

Its prime factorization is 545 = 5 × 109, with 109 prime. Accordingly, its divisors are 1, 5, 109, and 545. It is a semiprime, a product of two primes.

In base representations, 545 in decimal equals hex 0x221, octal 1041, and binary 1000100001.

Arithmetic properties include Euler’s totient φ(545) = 432, and the sum-of-divisors function σ(545) = 660.

In history, 545 CE falls in the mid-6th century, a period of Byzantine–Sassanian conflicts and the broader context of the Justinian plague era. Conversely, 545 BCE places the number in the late classical antiquity of the ancient world. The specific historical events associated with these years vary across regions and sources, but they are generally tied to the late antique geopolitics and demographic upheavals of the era.