It is a congruent number.
Almost surely, 221666844794232 is an apocalyptic number.
21666844794232 is a gapful number since it is divisible by the number (22) formed by its first and last digit.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21666844794232 is a wasteful number, since it uses less digits than its factorization.
21666844794232 is an evil number, because the sum of its binary digits is even.
The spelling of 21666844794232 in words is "twenty-one trillion, six hundred sixty-six billion, eight hundred forty-four million, seven hundred ninety-four thousand, two hundred thirty-two".