have someone's number

present singular third person has someone's number · participle present having someone's number · participle past had someone's number · past had someone's number · alternative get someone's number

1. idiomaticTo understand a person's character, capabilities, or situation.

   Morelli has her number: "Lots of energy, not much control, sexy as hell."

   1994 September 4, Marilyn Stasio, “Crime”, in The New York Times, →ISSN

   3 more examples

   "Whenever a person says to you that they are as innocent as can be in all concerning money, look well after your own money, for they are dead certain to collar it, if they can. Whenever a person proclaims to you ‘In worldly matters I’m a child,’ you consider that that person is only a crying off from being held accountable, and that you have got that person’s number, and it’s Number One."

   1852 March – 1853 September, Charles Dickens, chapter 57, in Bleak House, London: Bradbury and Evans, […], published 1853, →OCLC

   "Say! He's the hardest guy I ever saw," Stoner declared, admiringly. Mallow spoke last, but he spoke with conviction. "You said it, Brick. I had his number from the start. He's a master crook, and—it'll pay us all to string with him."

   1922, Rex Ellingwood Beach, chapter 10, in Flowing Gold

   Llodra, a doubles specialist who is ranked 38 in singles, was charging to the net at every opportunity and played some brilliant shots but Murray seemed to have his number at that stage.

   2008 August 28, “Tennis: Murray edges to win over Llodra”, in BBC Sport, retrieved 20 Nov 2009

2. Used other than figuratively or idiomatically: see have, someone's, number.