21113116021 has 2 divisors, whose sum is σ = 21113116022. Its totient is φ = 21113116020.

The previous prime is 21113115979. The next prime is 21113116033. The reversal of 21113116021 is 12061131112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21094367121 + 18748900 = 145239^2 + 4330^2 .

It is a cyclic number.

It is not a de Polignac number, because 21113116021 - 2¹⁵ = 21113083253 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21113116021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21113116621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556558010 + 10556558011.

It is an arithmetic number, because the mean of its divisors is an integer number (10556558011).

Almost surely, 2^21113116021 is an apocalyptic number.

It is an amenable number.

21113116021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21113116021 is an equidigital number, since it uses as much as digits as its factorization.

21113116021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 19.

Adding to 21113116021 its reverse (12061131112), we get a palindrome (33174247133).

The spelling of 21113116021 in words is "twenty-one billion, one hundred thirteen million, one hundred sixteen thousand, twenty-one".