21012111221009 has 2 divisors, whose sum is σ = 21012111221010. Its totient is φ = 21012111221008.

The previous prime is 21012111220951. The next prime is 21012111221107. The reversal of 21012111221009 is 90012211121012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12142715929600 + 8869395291409 = 3484640^2 + 2978153^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21012111221009 is a prime.

It is not a weakly prime, because it can be changed into another prime (21012111223009) 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, 10506055610504 + 10506055610505.

It is an arithmetic number, because the mean of its divisors is an integer number (10506055610505).

Almost surely, 2^{21012111221009} is an apocalyptic number.

It is an amenable number.

21012111221009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012111221009 is an equidigital number, since it uses as much as digits as its factorization.

21012111221009 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 23.

The spelling of 21012111221009 in words is "twenty-one trillion, twelve billion, one hundred eleven million, two hundred twenty-one thousand, nine".