221218 has 4 divisors (see below), whose sum is σ = 331830. Its totient is φ = 110608.

The previous prime is 221209. The next prime is 221219. The reversal of 221218 is 812122.

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

It can be written as a sum of positive squares in only one way, i.e., 146689 + 74529 = 383^2 + 273^2 .

It is not an unprimeable number, because it can be changed into a prime (221219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55303 + ... + 55306.

2²²¹²¹⁸ is an apocalyptic number.

221218 is a deficient number, since it is larger than the sum of its proper divisors (110612).

221218 is a wasteful number, since it uses less digits than its factorization.

221218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110611.

The product of its digits is 64, while the sum is 16.

The square root of 221218 is about 470.3381762094. The cubic root of 221218 is about 60.4793090003.

It can be divided in two parts, 22 and 1218, that multiplied together give a triangular number (26796 = T₂₃₁).

The spelling of 221218 in words is "two hundred twenty-one thousand, two hundred eighteen".