21203111221 has 2 divisors, whose sum is σ = 21203111222. Its totient is φ = 21203111220.

The previous prime is 21203111219. The next prime is 21203111233. The reversal of 21203111221 is 12211130212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19387499121 + 1815612100 = 139239^2 + 42610^2 .

It is a cyclic number.

It is not a de Polignac number, because 21203111221 - 2¹ = 21203111219 is a prime.

It is a super-2 number, since 2×21203111221² (a number of 21 digits) contains 22 as substring.

Together with 21203111219, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21203111195 and 21203111204.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21203111201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10601555610 + 10601555611.

It is an arithmetic number, because the mean of its divisors is an integer number (10601555611).

Almost surely, 2^21203111221 is an apocalyptic number.

It is an amenable number.

21203111221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21203111221 is an equidigital number, since it uses as much as digits as its factorization.

21203111221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21203111221 its reverse (12211130212), we get a palindrome (33414241433).

The spelling of 21203111221 in words is "twenty-one billion, two hundred three million, one hundred eleven thousand, two hundred twenty-one".