21305522261 has 2 divisors, whose sum is σ = 21305522262. Its totient is φ = 21305522260.

The previous prime is 21305522239. The next prime is 21305522279. The reversal of 21305522261 is 16222550312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15547596100 + 5757926161 = 124690^2 + 75881^2 .

It is a cyclic number.

It is not a de Polignac number, because 21305522261 - 2⁶ = 21305522197 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21305522461) 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, 10652761130 + 10652761131.

It is an arithmetic number, because the mean of its divisors is an integer number (10652761131).

Almost surely, 2^21305522261 is an apocalyptic number.

It is an amenable number.

21305522261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21305522261 is an equidigital number, since it uses as much as digits as its factorization.

21305522261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7200, while the sum is 29.

The spelling of 21305522261 in words is "twenty-one billion, three hundred five million, five hundred twenty-two thousand, two hundred sixty-one".