221666106565506 has 16 divisors (see below), whose sum is σ = 443332375666848. Its totient is φ = 73888675099200.

The previous prime is 221666106565489. The next prime is 221666106565609. The reversal of 221666106565506 is 605565601666122.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17834601 + ... + 27593571.

It is an arithmetic number, because the mean of its divisors is an integer number (27708273479178).

Almost surely, 2^{221666106565506} is an apocalyptic number.

221666106565506 is an abundant number, since it is smaller than the sum of its proper divisors (221666269101342).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221666106565506 is a wasteful number, since it uses less digits than its factorization.

221666106565506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13544657.

The product of its (nonzero) digits is 23328000, while the sum is 57.

The spelling of 221666106565506 in words is "two hundred twenty-one trillion, six hundred sixty-six billion, one hundred six million, five hundred sixty-five thousand, five hundred six".