It is a nude number because it is divisible by every one of its digits.
It is an Ulam number.
It is a self number, because there is not a number n which added to its sum of digits gives 421644.
2421644 is an apocalyptic number.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
421644 is a wasteful number, since it uses less digits than its factorization.
421644 is an evil number, because the sum of its binary digits is even.
The square root of 421644 is about 649.3412046066. The cubic root of 421644 is about 74.9863086119.
Adding to 421644 its reverse (446124), we get a palindrome (867768).
The spelling of 421644 in words is "four hundred twenty-one thousand, six hundred forty-four".