21221120021 has 2 divisors, whose sum is σ = 21221120022. Its totient is φ = 21221120020.

The previous prime is 21221120003. The next prime is 21221120027. The reversal of 21221120021 is 12002112212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12150652900 + 9070467121 = 110230^2 + 95239^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221120021 - 2⁶ = 21221119957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21221119978 and 21221120005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221120027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610560010 + 10610560011.

It is an arithmetic number, because the mean of its divisors is an integer number (10610560011).

Almost surely, 2^21221120021 is an apocalyptic number.

It is an amenable number.

21221120021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221120021 is an equidigital number, since it uses as much as digits as its factorization.

21221120021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21221120021 its reverse (12002112212), we get a palindrome (33223232233).

It can be divided in two parts, 212211 and 20021, that added together give a palindrome (232232).

The spelling of 21221120021 in words is "twenty-one billion, two hundred twenty-one million, one hundred twenty thousand, twenty-one".