21201212009 has 2 divisors, whose sum is σ = 21201212010. Its totient is φ = 21201212008.

The previous prime is 21201211991. The next prime is 21201212027. The reversal of 21201212009 is 90021210212.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21201211991) and next prime (21201212027).

It can be written as a sum of positive squares in only one way, i.e., 21033120784 + 168091225 = 145028^2 + 12965^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201212009 - 2²⁰ = 21200163433 is a prime.

It is not a weakly prime, because it can be changed into another prime (21201212029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600606004 + 10600606005.

It is an arithmetic number, because the mean of its divisors is an integer number (10600606005).

Almost surely, 2^21201212009 is an apocalyptic number.

It is an amenable number.

21201212009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201212009 is an equidigital number, since it uses as much as digits as its factorization.

21201212009 is an odious number, because the sum of its binary digits is odd.

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

The spelling of 21201212009 in words is "twenty-one billion, two hundred one million, two hundred twelve thousand, nine".