21211212109 has 2 divisors, whose sum is σ = 21211212110. Its totient is φ = 21211212108.

The previous prime is 21211212107. The next prime is 21211212133. The reversal of 21211212109 is 90121211212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16448832009 + 4762380100 = 128253^2 + 69010^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211212109 - 2¹ = 21211212107 is a prime.

Together with 21211212107, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21211212109.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21211212107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605606054 + 10605606055.

It is an arithmetic number, because the mean of its divisors is an integer number (10605606055).

Almost surely, 2^21211212109 is an apocalyptic number.

It is an amenable number.

21211212109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211212109 is an equidigital number, since it uses as much as digits as its factorization.

21211212109 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 22.

The spelling of 21211212109 in words is "twenty-one billion, two hundred eleven million, two hundred twelve thousand, one hundred nine".