21155055109 has 2 divisors, whose sum is σ = 21155055110. Its totient is φ = 21155055108.

The previous prime is 21155055079. The next prime is 21155055113. The reversal of 21155055109 is 90155055112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20729664484 + 425390625 = 143978^2 + 20625^2 .

It is a cyclic number.

It is not a de Polignac number, because 21155055109 - 2¹³ = 21155046917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21155055709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577527554 + 10577527555.

It is an arithmetic number, because the mean of its divisors is an integer number (10577527555).

Almost surely, 2^21155055109 is an apocalyptic number.

It is an amenable number.

21155055109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155055109 is an equidigital number, since it uses as much as digits as its factorization.

21155055109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11250, while the sum is 34.

The spelling of 21155055109 in words is "twenty-one billion, one hundred fifty-five million, fifty-five thousand, one hundred nine".