21101220109 has 2 divisors, whose sum is σ = 21101220110. Its totient is φ = 21101220108.

The previous prime is 21101220103. The next prime is 21101220163. The reversal of 21101220109 is 90102210112.

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., 19859010084 + 1242210025 = 140922^2 + 35245^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101220109 - 2⁹ = 21101219597 is a prime.

It is a super-2 number, since 2×21101220109² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101220103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550610054 + 10550610055.

It is an arithmetic number, because the mean of its divisors is an integer number (10550610055).

Almost surely, 2^21101220109 is an apocalyptic number.

It is an amenable number.

21101220109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101220109 is an equidigital number, since it uses as much as digits as its factorization.

21101220109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 19.

The spelling of 21101220109 in words is "twenty-one billion, one hundred one million, two hundred twenty thousand, one hundred nine".