27421 is a product of two 4K+1 primes and so it can be expressed as a sum of two squares in two different ways viz. 14^2 + 165^2 and 90^2 + 139^2.

27421 is a member of OEIS A107085: numbers n such that in decimal representation the largest digit is equal to the digital root, here 7. See entry for 27340.

27421 is a number with sums of odd and even numbers both equal to 8. It is thus an "attractor" that "attracts" only one other number viz. 27397 where we see that -2 + 7 + 3 + 9 + 7 = 24 and 27397 + 24 = 27421. Permalink.

27421 forms a pair with 27422: pairs of semiprimes whose sums of prime factors both contain three or more 1's. There are only eleven such pairs in the range up to 100,000.

27421 is a cyclic and Duffinian number.

27421 is a junction number because it is equal to n + sod(n) for n = 27395 and 27404.

27421 can be written as a digit equation as follows:

2 + 7 = 4 * 2 + 1

27421 stabilises after about 60 generations of Conway's Game of Life to a single glider, a single traffic light oscillator and two still life blocks.