211211221 has 8 divisors (see below), whose sum is σ = 227667384. Its totient is φ = 194784960.

The previous prime is 211211191. The next prime is 211211243. The reversal of 211211221 is 122112112.

It can be written as a sum of positive squares in 4 ways, for example, as 4972900 + 206238321 = 2230^2 + 14361^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 211211221 - 2⁹ = 211210709 is a prime.

It is a super-2 number, since 2×211211221² = 89220359752621682, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211211251) 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, 8475 + ... + 22231.

It is an arithmetic number, because the mean of its divisors is an integer number (28458423).

Almost surely, 2^211211221 is an apocalyptic number.

It is an amenable number.

211211221 is a deficient number, since it is larger than the sum of its proper divisors (16456163).

211211221 is a wasteful number, since it uses less digits than its factorization.

211211221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14951.

The product of its digits is 16, while the sum is 13.

The square root of 211211221 is about 14533.1077543655. The cubic root of 211211221 is about 595.5327676407.

Adding to 211211221 its reverse (122112112), we get a palindrome (333323333).

The spelling of 211211221 in words is "two hundred eleven million, two hundred eleven thousand, two hundred twenty-one".