21013000109 has 2 divisors, whose sum is σ = 21013000110. Its totient is φ = 21013000108.

The previous prime is 21013000081. The next prime is 21013000139. The reversal of 21013000109 is 90100031012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18057446884 + 2955553225 = 134378^2 + 54365^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21013000109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21013000139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506500054 + 10506500055.

It is an arithmetic number, because the mean of its divisors is an integer number (10506500055).

Almost surely, 2^21013000109 is an apocalyptic number.

It is an amenable number.

21013000109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21013000109 is an equidigital number, since it uses as much as digits as its factorization.

21013000109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 54, while the sum is 17.

The spelling of 21013000109 in words is "twenty-one billion, thirteen million, one hundred nine", and thus it is an aban number.