It is a sphenic number, since it is the product of 3 distinct primes.
It is a congruent number.
It is an unprimeable number.
221742 is an apocalyptic number.
21742 is a wasteful number, since it uses less digits than its factorization.
21742 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1562.
The square root of 21742 is about 147.4516870029. The cubic root of 21742 is about 27.9104280508.
The spelling of 21742 in words is "twenty-one thousand, seven hundred forty-two", and thus it is an iban number.