21205522553 has 2 divisors, whose sum is σ = 21205522554. Its totient is φ = 21205522552.

The previous prime is 21205522531. The next prime is 21205522561. The reversal of 21205522553 is 35522550212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18016887529 + 3188635024 = 134227^2 + 56468^2 .

It is a cyclic number.

It is not a de Polignac number, because 21205522553 - 2¹² = 21205518457 is a prime.

It is not a weakly prime, because it can be changed into another prime (21205522153) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602761276 + 10602761277.

It is an arithmetic number, because the mean of its divisors is an integer number (10602761277).

Almost surely, 2^21205522553 is an apocalyptic number.

It is an amenable number.

21205522553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21205522553 is an equidigital number, since it uses as much as digits as its factorization.

21205522553 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30000, while the sum is 32.

The spelling of 21205522553 in words is "twenty-one billion, two hundred five million, five hundred twenty-two thousand, five hundred fifty-three".