21021102209 has 2 divisors, whose sum is σ = 21021102210. Its totient is φ = 21021102208.

The previous prime is 21021102107. The next prime is 21021102283. The reversal of 21021102209 is 90220112012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19475039809 + 1546062400 = 139553^2 + 39320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021102209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021102299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510551104 + 10510551105.

It is an arithmetic number, because the mean of its divisors is an integer number (10510551105).

Almost surely, 2^21021102209 is an apocalyptic number.

It is an amenable number.

21021102209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021102209 is an equidigital number, since it uses as much as digits as its factorization.

21021102209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 21021102209 in words is "twenty-one billion, twenty-one million, one hundred two thousand, two hundred nine".