It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-21661465732411 is a prime.
It is a Duffinian number.
Almost surely, 221661465732411 is an apocalyptic number.
21661465732411 is an equidigital number, since it uses as much as digits as its factorization.
21661465732411 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 5379061820.
The spelling of 21661465732411 in words is "twenty-one trillion, six hundred sixty-one billion, four hundred sixty-five million, seven hundred thirty-two thousand, four hundred eleven".