1623 = 3 x 541.
1623 is a number for which the sum of the reciprocals of its digits is an integer (A034708).
1623 is a number whose product of digits is three times the sum of its digits (A062035).
1623 is a semiprime that is the sum of three consecutive semiprimes (A131610).
1623 is a number that is not the sum of two triangular numbers and a fourth power (A115160).
1623 cannot be written as the sum of three squares.
1623 divides 524 - 1.