21002121211 has 4 divisors (see below), whose sum is σ = 21679609024. Its totient is φ = 20324633400.

The previous prime is 21002121193. The next prime is 21002121223. The reversal of 21002121211 is 11212120012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002121211 is a prime.

It is a super-2 number, since 2×21002121211² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002121191 and 21002121200.

It is not an unprimeable number, because it can be changed into a prime (21002121271) 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, 338743860 + ... + 338743921.

It is an arithmetic number, because the mean of its divisors is an integer number (5419902256).

Almost surely, 2^21002121211 is an apocalyptic number.

21002121211 is a deficient number, since it is larger than the sum of its proper divisors (677487813).

21002121211 is an equidigital number, since it uses as much as digits as its factorization.

21002121211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 677487812.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21002121211 its reverse (11212120012), we get a palindrome (32214241223).

The spelling of 21002121211 in words is "twenty-one billion, two million, one hundred twenty-one thousand, two hundred eleven".