Can anyone identify this encryption method and can anyone tell me if this is secure?

"antionline" is encrypted as: "21566248525351475139"

Can you please tell me if this is a known algorithm since I have never seen this before.

Another text that has been encrypted that way, which I’m trying to figure out, is: "423755394574895052713266896225412357"

Thanks in advance and any help or advice will be greatly appreciated.

Qwert1515