Published online by Cambridge University Press: 18 January 2021
Let G be a finite group and
$\chi $
be a character of G. The codegree of
$\chi $
is
${{\operatorname{codeg}}} (\chi ) ={|G: \ker \chi |}/{\chi (1)}$
. We write
$\pi (G)$
for the set of prime divisors of
$|G|$
,
$\pi ({{\operatorname{codeg}}} (\chi ))$
for the set of prime divisors of
${{\operatorname{codeg}}} (\chi )$
and
$\sigma ({{\operatorname{codeg}}} (G))= \max \{|\pi ({{\operatorname{codeg}}} (\chi ))| : \chi \in {\textrm {Irr}}(G)\}$
. We show that
$|\pi (G)| \leq ({23}/{3}) \sigma ({{\operatorname{codeg}}} (G))$
. This improves the main result of Yang and Qian [‘The analog of Huppert’s conjecture on character codegrees’, J. Algebra478 (2017), 215–219].
This work was partially supported by the NSF of China (No. 11671063) and a grant from the Simons Foundation (No. 499532).