21013245109 has 2 divisors, whose sum is σ = 21013245110. Its totient is φ = 21013245108.

The previous prime is 21013245107. The next prime is 21013245151. The reversal of 21013245109 is 90154231012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18415304209 + 2597940900 = 135703^2 + 50970^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013245109 - 2¹ = 21013245107 is a prime.

Together with 21013245107, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21013245101) 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, 10506622554 + 10506622555.

It is an arithmetic number, because the mean of its divisors is an integer number (10506622555).

Almost surely, 2^21013245109 is an apocalyptic number.

It is an amenable number.

21013245109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21013245109 is an equidigital number, since it uses as much as digits as its factorization.

21013245109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 28.

The spelling of 21013245109 in words is "twenty-one billion, thirteen million, two hundred forty-five thousand, one hundred nine".