21000553109 has 2 divisors, whose sum is σ = 21000553110. Its totient is φ = 21000553108.

The previous prime is 21000553039. The next prime is 21000553157. The reversal of 21000553109 is 90135500012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20612344900 + 388208209 = 143570^2 + 19703^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000553109 - 2¹² = 21000549013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000558109) 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, 10500276554 + 10500276555.

It is an arithmetic number, because the mean of its divisors is an integer number (10500276555).

Almost surely, 2^21000553109 is an apocalyptic number.

It is an amenable number.

21000553109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000553109 is an equidigital number, since it uses as much as digits as its factorization.

21000553109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1350, while the sum is 26.

The spelling of 21000553109 in words is "twenty-one billion, five hundred fifty-three thousand, one hundred nine".