21213123211 has 16 divisors (see below), whose sum is σ = 25806297600. Its totient is φ = 17032137408.

The previous prime is 21213123187. The next prime is 21213123229. The reversal of 21213123211 is 11232131212.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21213123211 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is not an unprimeable number, because it can be changed into a prime (21213123241) 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, 884215 + ... + 907888.

It is an arithmetic number, because the mean of its divisors is an integer number (1612893600).

Almost surely, 2^21213123211 is an apocalyptic number.

21213123211 is a deficient number, since it is larger than the sum of its proper divisors (4593174389).

21213123211 is a wasteful number, since it uses less digits than its factorization.

21213123211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1792218.

The product of its digits is 144, while the sum is 19.

Adding to 21213123211 its reverse (11232131212), we get a palindrome (32445254423).

The spelling of 21213123211 in words is "twenty-one billion, two hundred thirteen million, one hundred twenty-three thousand, two hundred eleven".