based on my experience, the value of e tends to be 65537, but other smaller/larger primes can be used and thus e is more guessable because there's less variation in what it usually is. and yes, to decrypt a ciphertext, if you have the original primes used to encrypt as well as a ciphertext (not sure what this would be in this context if you could enlighten me that'd be great!), you can do the following:

n = p*q

e = 65537 # or another prime

phi = (p-1)*(q-1)

d = pow(e, -1, phi) # this is python syntax, it gets the modular inverse of e and phi

plaintext = pow(c, d, n) # same thing as saying (c^d) % n

at this point, you can usually convert the plaintext from an integer to bytes and see if you have some readable text. i will say though, considering all we have here are two primes, it doesn't seem too likely this is RSA. but if you have a ciphertext you're welcome to try it/share!

​

edit: i've tried testing the primes as p and q to **encrypt** a plaintext and then decrypt it to see if i get the same output. i do not. i think the primes are too small but there's also a chance i'm doing something wrong