21111031021 has 2 divisors, whose sum is σ = 21111031022. Its totient is φ = 21111031020.

The previous prime is 21111031003. The next prime is 21111031037. The reversal of 21111031021 is 12013011112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18147861796 + 2963169225 = 134714^2 + 54435^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111031021 - 2¹¹ = 21111028973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21111030992 and 21111031010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111031061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555515510 + 10555515511.

It is an arithmetic number, because the mean of its divisors is an integer number (10555515511).

Almost surely, 2^21111031021 is an apocalyptic number.

It is an amenable number.

21111031021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111031021 is an equidigital number, since it uses as much as digits as its factorization.

21111031021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12, while the sum is 13.

Adding to 21111031021 its reverse (12013011112), we get a palindrome (33124042133).

The spelling of 21111031021 in words is "twenty-one billion, one hundred eleven million, thirty-one thousand, twenty-one".