21201010209 has 6 divisors (see below), whose sum is σ = 30623681426. Its totient is φ = 14134006800.

The previous prime is 21201010189. The next prime is 21201010213. The reversal of 21201010209 is 90201010212.

It can be written as a sum of positive squares in only one way, i.e., 15221390625 + 5979619584 = 123375^2 + 77328^2 .

It is not a de Polignac number, because 21201010209 - 2²⁰ = 21199961633 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21201010191 and 21201010200.

It is not an unprimeable number, because it can be changed into a prime (21201010279) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1177833892 + ... + 1177833909.

Almost surely, 2^21201010209 is an apocalyptic number.

It is an amenable number.

21201010209 is a deficient number, since it is larger than the sum of its proper divisors (9422671217).

21201010209 is a wasteful number, since it uses less digits than its factorization.

21201010209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2355667807 (or 2355667804 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The spelling of 21201010209 in words is "twenty-one billion, two hundred one million, ten thousand, two hundred nine".