3642 = 2 x 3 x 607.
3642 is 320322 in base 4 and 7072 in base 8.
3642 is the number of labeled topologies with 5 points.
3642 and 36422 use only the digits 1, 2, 3, 4, and 6. The internal digits of the squared number include only the digits of the number.
36423641 and 36423643 are a pair of twin primes.