21221211 has 16 divisors (see below), whose sum is σ = 31177728. Its totient is φ = 12732000.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221211 is 11212212.

It is not a de Polignac number, because 21221211 - 2²¹ = 19124059 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21221251) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 150 + ... + 6516.

It is an arithmetic number, because the mean of its divisors is an integer number (1948608).

Almost surely, 2^21221211 is an apocalyptic number.

21221211 is a deficient number, since it is larger than the sum of its proper divisors (9956517).

21221211 is a wasteful number, since it uses less digits than its factorization.

21221211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6482.

The product of its digits is 16, while the sum is 12.

The square root of 21221211 is about 4606.6485648462. The cubic root of 21221211 is about 276.8577729975.

Adding to 21221211 its reverse (11212212), we get a palindrome (32433423).

It can be divided in two parts, 212212 and 11, that multiplied together give a palindrome (2334332).

The spelling of 21221211 in words is "twenty-one million, two hundred twenty-one thousand, two hundred eleven".