221857 has 4 divisors (see below), whose sum is σ = 225556. Its totient is φ = 218160.

The previous prime is 221849. The next prime is 221873. The reversal of 221857 is 758122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6561 + 215296 = 81^2 + 464^2 .

It is a cyclic number.

It is not a de Polignac number, because 221857 - 2³ = 221849 is a prime.

It is a Duffinian number.

221857 is a lucky number.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (221807) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1758 + ... + 1879.

It is an arithmetic number, because the mean of its divisors is an integer number (56389).

2²²¹⁸⁵⁷ is an apocalyptic number.

It is an amenable number.

221857 is a deficient number, since it is larger than the sum of its proper divisors (3699).

221857 is an equidigital number, since it uses as much as digits as its factorization.

221857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3698.

The product of its digits is 1120, while the sum is 25.

The square root of 221857 is about 471.0169848318. The cubic root of 221857 is about 60.5374855915.

Adding to 221857 its reverse (758122), we get a palindrome (979979).

The spelling of 221857 in words is "two hundred twenty-one thousand, eight hundred fifty-seven".