[bilky asko]

Interesting… love that there’s an app for people wanting to do it

However this wouldn’t explain the BGT act as he got everyone in the audience and at home to do the maths alongside him on their regular calculator apps

I'm going to have to watch it now...

EDIT: It seems it is performed differently to the Mulhern trick, as Dec produces the six-digit number.

You could still do the maths yourself with Mulhern's trick, as he instructed Holly Willoughby and her cohost to do.

In this case, the simplest explanation was that Dec was told the correct number to read, which might explain the slightly odd way he spoke it. Not that it's definitely the way it was done!