221505566655 has 16 divisors (see below), whose sum is σ = 375256489824. Its totient is φ = 111187107840.

The previous prime is 221505566651. The next prime is 221505566717. The reversal of 221505566655 is 556665505122.

It is not a de Polignac number, because 221505566655 - 2² = 221505566651 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221505566651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 434324386 + ... + 434324895.

It is an arithmetic number, because the mean of its divisors is an integer number (23453530614).

Almost surely, 2^221505566655 is an apocalyptic number.

221505566655 is a deficient number, since it is larger than the sum of its proper divisors (153750923169).

221505566655 is a wasteful number, since it uses less digits than its factorization.

221505566655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 868649306.

The product of its (nonzero) digits is 2700000, while the sum is 48.

The spelling of 221505566655 in words is "two hundred twenty-one billion, five hundred five million, five hundred sixty-six thousand, six hundred fifty-five".