221666655 has 32 divisors (see below), whose sum is σ = 429179904. Its totient is φ = 95371776.

The previous prime is 221666629. The next prime is 221666659. The reversal of 221666655 is 556666122.

It is a happy number.

It is not a de Polignac number, because 221666655 - 2⁷ = 221666527 is a prime.

It is a super-2 number, since 2×221666655² = 98272211877778050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221666659) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 60307 + ... + 63876.

It is an arithmetic number, because the mean of its divisors is an integer number (13411872).

Almost surely, 2^221666655 is an apocalyptic number.

221666655 is a deficient number, since it is larger than the sum of its proper divisors (207513249).

221666655 is a wasteful number, since it uses less digits than its factorization.

221666655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124215.

The product of its digits is 129600, while the sum is 39.

The square root of 221666655 is about 14888.4738976162. The cubic root of 221666655 is about 605.2016767246.

The spelling of 221666655 in words is "two hundred twenty-one million, six hundred sixty-six thousand, six hundred fifty-five".