λεληθότως
From LSJ
τὸ πλῆθος οὐκ εὐαρίθμητον ἦν → the crowd wasn't easy to count, the crowd was not small, it was not a small crowd
English (LSJ)
Adv. pf. part. of λανθάνω,
A imperceptibly, Pl.Ax.365c, Cic.Att.6.5.3, Fam.9.2.3, D.H.Comp.22, Anacreont.15.16, Luc.Am. 13; secretly, LXX 2 Ma.6.11, 8.1.
German (Pape)
[Seite 28] adv. zum part. perf. von λανθάνω, heimlich, unvermerkt, Plat. Ax. 365 c u. Sp., von Hdn. für κρύφα verworfen.