21661630166 has 32 divisors (see below), whose sum is σ = 36092770560. Its totient is φ = 9667045600.

The previous prime is 21661630147. The next prime is 21661630169. The reversal of 21661630166 is 66103616612.

It is a super-2 number, since 2×21661630166² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661630169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1055495 + ... + 1075821.

It is an arithmetic number, because the mean of its divisors is an integer number (1127899080).

Almost surely, 2^21661630166 is an apocalyptic number.

21661630166 is a deficient number, since it is larger than the sum of its proper divisors (14431140394).

21661630166 is a wasteful number, since it uses less digits than its factorization.

21661630166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21220.

The product of its (nonzero) digits is 46656, while the sum is 38.

The spelling of 21661630166 in words is "twenty-one billion, six hundred sixty-one million, six hundred thirty thousand, one hundred sixty-six".