21011211211 has 4 divisors (see below), whose sum is σ = 21020707872. Its totient is φ = 21001714552.

The previous prime is 21011211187. The next prime is 21011211241. The reversal of 21011211211 is 11211211012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21011211211 - 2¹⁹ = 21010686923 is a prime.

It is a super-3 number, since 3×21011211211³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011211191 and 21011211200.

It is not an unprimeable number, because it can be changed into a prime (21011211241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4745011 + ... + 4749436.

It is an arithmetic number, because the mean of its divisors is an integer number (5255176968).

Almost surely, 2^21011211211 is an apocalyptic number.

21011211211 is a deficient number, since it is larger than the sum of its proper divisors (9496661).

21011211211 is an equidigital number, since it uses as much as digits as its factorization.

21011211211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9496660.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21011211211 its reverse (11211211012), we get a palindrome (32222422223).

The spelling of 21011211211 in words is "twenty-one billion, eleven million, two hundred eleven thousand, two hundred eleven".