21211222221 has 80 divisors (see below), whose sum is σ = 36673415680. Its totient is φ = 11967264000.

The previous prime is 21211222217. The next prime is 21211222231. The reversal of 21211222221 is 12222211212.

It is a happy number.

21211222221 is a `hidden beast` number, since 212 + 11 + 222 + 221 = 666.

It is not a de Polignac number, because 21211222221 - 2² = 21211222217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21211222194 and 21211222203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211222231) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 28243596 + ... + 28244346.

It is an arithmetic number, because the mean of its divisors is an integer number (458417696).

Almost surely, 2^21211222221 is an apocalyptic number.

21211222221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21211222221 is a deficient number, since it is larger than the sum of its proper divisors (15462193459).

21211222221 is a wasteful number, since it uses less digits than its factorization.

21211222221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1336 (or 1327 counting only the distinct ones).

The product of its digits is 128, while the sum is 18.

Adding to 21211222221 its reverse (12222211212), we get a palindrome (33433433433).

The spelling of 21211222221 in words is "twenty-one billion, two hundred eleven million, two hundred twenty-two thousand, two hundred twenty-one".