773 is a prime number.

A prime number has only two positive divisors: 1 and itself.

For 773, the positive divisors are :

• 1 is a divisor of 773 : $773 / 1 = 773$
• 773 is a divisor of 773 : $773 / 773 = 1$

773 has only two divisors, 1 and itself.
Therefore, 773 is a prime number.