21021111211 has 4 divisors (see below), whose sum is σ = 21935072592. Its totient is φ = 20107149832.

The previous prime is 21021111203. The next prime is 21021111227. The reversal of 21021111211 is 11211112012.

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 21021111211 - 2³ = 21021111203 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021111191 and 21021111200.

It is not an unprimeable number, because it can be changed into a prime (21021111311) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 456980656 + ... + 456980701.

It is an arithmetic number, because the mean of its divisors is an integer number (5483768148).

Almost surely, 2^21021111211 is an apocalyptic number.

21021111211 is a deficient number, since it is larger than the sum of its proper divisors (913961381).

21021111211 is an equidigital number, since it uses as much as digits as its factorization.

21021111211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 913961380.

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

Adding to 21021111211 its reverse (11211112012), we get a palindrome (32232223223).

The spelling of 21021111211 in words is "twenty-one billion, twenty-one million, one hundred eleven thousand, two hundred eleven".