3639

3639 = 3 x 1213.

Concatenating the distinct prime factors of 3639 produces a palindrome (A046448): 31213.

3639 is a member of the Fibonacci-like sequence beginning with 1 and 15 (A022105).

The square of 3639 contains only the digits 1, 2, 3, and 4 (A061677).

3639 divides 47¹² - 1.

3639 is a number that cannot be written as a sum of three squares.

Source: OEIS