21011020111 has 2 divisors, whose sum is σ = 21011020112. Its totient is φ = 21011020110.

The previous prime is 21011020067. The next prime is 21011020123. The reversal of 21011020111 is 11102011012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21011020111 - 2³³ = 12421085519 is a prime.

It is a super-2 number, since 2×21011020111² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011020141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505510055 + 10505510056.

It is an arithmetic number, because the mean of its divisors is an integer number (10505510056).

Almost surely, 2^21011020111 is an apocalyptic number.

21011020111 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011020111 is an equidigital number, since it uses as much as digits as its factorization.

21011020111 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4, while the sum is 10.

Adding to 21011020111 its reverse (11102011012), we get a palindrome (32113031123).

Subtracting from 21011020111 its reverse (11102011012), we obtain a palindrome (9909009099).

The spelling of 21011020111 in words is "twenty-one billion, eleven million, twenty thousand, one hundred eleven".