What is "incongruous numbers"

Incongruous \In*con"gru*ous\, a. [L. incongruus. See In- not, and Congruous.] Not congruous; reciprocally disagreeing; not capable of harmonizing or readily assimilating; inharmonious; inappropriate; unsuitable; not fitting; inconsistent; improper; as, an incongruous remark; incongruous behavior, action, dress, etc. ``Incongruous mixtures of opinions.''
--I. Taylor. ``Made up of incongruous parts.''
--Macaulay.

Incongruous denotes that kind of absence of harmony or suitableness of which the taste and experience of men takes cognizance.
--C. J. Smith.

Incongruous numbers (Arith.), two numbers, which, with respect to a third, are such that their difference can not be divided by it without a remainder, the two numbers being said to be incongruous with respect to the third; as, twenty and twenty-five are incongruous with respect to four.

Syn: Inconsistent; unsuitable; inharmonious; disagreeing; absurd; inappropriate; unfit; improper. See Inconsistent. -- In*con"gru*ous*ly, adv. -- In*con"gru*ous*ness, n.