21002010209 has 2 divisors, whose sum is σ = 21002010210. Its totient is φ = 21002010208.

The previous prime is 21002010199. The next prime is 21002010229. The reversal of 21002010209 is 90201020012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11548726225 + 9453283984 = 107465^2 + 97228^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002010209 - 2²⁰ = 21000961633 is a prime.

It is not a weakly prime, because it can be changed into another prime (21002010229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501005104 + 10501005105.

It is an arithmetic number, because the mean of its divisors is an integer number (10501005105).

Almost surely, 2^21002010209 is an apocalyptic number.

It is an amenable number.

21002010209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002010209 is an equidigital number, since it uses as much as digits as its factorization.

21002010209 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 17.

The spelling of 21002010209 in words is "twenty-one billion, two million, ten thousand, two hundred nine".