21135874021 has 2 divisors, whose sum is σ = 21135874022. Its totient is φ = 21135874020.

The previous prime is 21135873991. The next prime is 21135874049. The reversal of 21135874021 is 12047853112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18214471521 + 2921402500 = 134961^2 + 54050^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135874021 - 2¹¹ = 21135871973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21135874051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567937010 + 10567937011.

It is an arithmetic number, because the mean of its divisors is an integer number (10567937011).

Almost surely, 2^21135874021 is an apocalyptic number.

It is an amenable number.

21135874021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135874021 is an equidigital number, since it uses as much as digits as its factorization.

21135874021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13440, while the sum is 34.

The spelling of 21135874021 in words is "twenty-one billion, one hundred thirty-five million, eight hundred seventy-four thousand, twenty-one".