smallest Deletable Prime greater than 443

[Nekkamath]

A "deletable prime" is a positive integer that (1) is prime and (2) is either a one digit integer or, after removing one digit, results in another deletable prime. For example, 439 is deletable because 439 is prime and deleting the 9 results in another deletable prime, 43, which is deletable because removing the 4 results in the prime 3. What is the smallest deletable prime larger than 443?

I say the answer is 447: by removing the 4 you get 47 and by removing the next 4 you get 7.

 

[tkhunny]

You'll have to do better than that. 447 = 3*149

 

[Nekkamath]

Thanks. You are right.

 

[Nekkamath]

How about 457?

 

[tkhunny]

Can you prove it or did you just pull it out of a hat?

 

[Nekkamath]

I did pull it out of the hat, the hat of prime numbers. But I did not do the math.

So I change my answer to 467. When you drop the 4, you get 67 a prime number. When you drop the 6 of the 67, you get 7 a prime number.

The next number would be 479. When you drop the 4 you get 79 a prime number. When you drop the 9 from 79 you get 7 a prime number.

How is that?

 

[pka]

How about 457?

Why not stick to your guns?
In 457 delete 5 and get 47.
Then delete 4 and get 7.

 

[Nekkamath]

I see, I see. Thanks.