221205657 has 8 divisors (see below), whose sum is σ = 310464160. Its totient is φ = 139708800.

The previous prime is 221205637. The next prime is 221205661. The reversal of 221205657 is 756502122.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 221205657 - 2⁷ = 221205529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221205617) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1940344 + ... + 1940457.

It is an arithmetic number, because the mean of its divisors is an integer number (38808020).

Almost surely, 2^221205657 is an apocalyptic number.

It is an amenable number.

221205657 is a deficient number, since it is larger than the sum of its proper divisors (89258503).

221205657 is a wasteful number, since it uses less digits than its factorization.

221205657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3880823.

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 221205657 is about 14872.9841323118. The cubic root of 221205657 is about 604.7818415216.

Adding to 221205657 its reverse (756502122), we get a palindrome (977707779).

The spelling of 221205657 in words is "two hundred twenty-one million, two hundred five thousand, six hundred fifty-seven".