In a polite way, you can decline sharing your number by saying something like:
"I appreciate your interest, but I prefer to keep my personal contact information private."
"I'm sorry, but I don't feel comfortable sharing my number at the moment."
"Thank you for asking, but I'd rather not give out my number right now."
"I hope you understand, but I'd prefer not to share my contact details."
"I'm sorry, but I'd rather not exchange numbers at this time."
Please note that it's essential to be assertive yet respectful when declining such requests to maintain a friendly and courteous tone.