1623

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.

Source: OEIS