21211021211209 has 2 divisors, whose sum is σ = 21211021211210. Its totient is φ = 21211021211208.

The previous prime is 21211021211183. The next prime is 21211021211243. The reversal of 21211021211209 is 90211212011212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17756616099600 + 3454405111609 = 4213860^2 + 1858603^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211021211209 is a prime.

It is a super-2 number, since 2×21211021211209² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21211021211509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605510605604 + 10605510605605.

It is an arithmetic number, because the mean of its divisors is an integer number (10605510605605).

Almost surely, 2^{21211021211209} is an apocalyptic number.

It is an amenable number.

21211021211209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211021211209 is an equidigital number, since it uses as much as digits as its factorization.

21211021211209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 25.

The spelling of 21211021211209 in words is "twenty-one trillion, two hundred eleven billion, twenty-one million, two hundred eleven thousand, two hundred nine".