21809553629 has 2 divisors, whose sum is σ = 21809553630. Its totient is φ = 21809553628.

The previous prime is 21809553613. The next prime is 21809553631. The reversal of 21809553629 is 92635590812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20880828004 + 928725625 = 144502^2 + 30475^2 .

It is a cyclic number.

It is not a de Polignac number, because 21809553629 - 2⁴ = 21809553613 is a prime.

Together with 21809553631, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21809523629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10904776814 + 10904776815.

It is an arithmetic number, because the mean of its divisors is an integer number (10904776815).

Almost surely, 2^21809553629 is an apocalyptic number.

It is an amenable number.

21809553629 is a deficient number, since it is larger than the sum of its proper divisors (1).

21809553629 is an equidigital number, since it uses as much as digits as its factorization.

21809553629 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1166400, while the sum is 50.

The spelling of 21809553629 in words is "twenty-one billion, eight hundred nine million, five hundred fifty-three thousand, six hundred twenty-nine".