The public exponent e is published with RSA’s public parameters and raises a message to a power modulo the public modulus during encryption. A small exponent makes encryption fast; 65,537 is a historically common choice. section 6.3.1
A tiny RSA calculation
With message m = 2, public exponent e = 2, and modulus p = 5, encryption computes ciphertext = 2² mod 5 = 4. Real RSA uses a public modulus N = p × q rather than a single prime. section 6.3.1

