21213109 has 2 divisors, whose sum is σ = 21213110. Its totient is φ = 21213108.

The previous prime is 21213097. The next prime is 21213119. The reversal of 21213109 is 90131212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20958084 + 255025 = 4578^2 + 505^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213109 - 2¹³ = 21204917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21213119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606554 + 10606555.

It is an arithmetic number, because the mean of its divisors is an integer number (10606555).

Almost surely, 2^21213109 is an apocalyptic number.

It is an amenable number.

21213109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213109 is an equidigital number, since it uses as much as digits as its factorization.

21213109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21213109 is about 4605.7690997270. The cubic root of 21213109 is about 276.8225348703.

The spelling of 21213109 in words is "twenty-one million, two hundred thirteen thousand, one hundred nine".