21220109 has 2 divisors, whose sum is σ = 21220110. Its totient is φ = 21220108.

The previous prime is 21220103. The next prime is 21220153. The reversal of 21220109 is 90102212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15976009 + 5244100 = 3997^2 + 2290^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220109 - 2⁸ = 21219853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610054 + 10610055.

It is an arithmetic number, because the mean of its divisors is an integer number (10610055).

Almost surely, 2^21220109 is an apocalyptic number.

It is an amenable number.

21220109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220109 is an equidigital number, since it uses as much as digits as its factorization.

21220109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21220109 is about 4606.5289535615. The cubic root of 21220109 is about 276.8529805825.

The spelling of 21220109 in words is "twenty-one million, two hundred twenty thousand, one hundred nine".