21445187521 has 2 divisors, whose sum is σ = 21445187522. Its totient is φ = 21445187520.

The previous prime is 21445187509. The next prime is 21445187527. The reversal of 21445187521 is 12578154412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21332063025 + 113124496 = 146055^2 + 10636^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21445187521 is a prime.

It is not a weakly prime, because it can be changed into another prime (21445187527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10722593760 + 10722593761.

It is an arithmetic number, because the mean of its divisors is an integer number (10722593761).

Almost surely, 2^21445187521 is an apocalyptic number.

It is an amenable number.

21445187521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21445187521 is an equidigital number, since it uses as much as digits as its factorization.

21445187521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 89600, while the sum is 40.

The spelling of 21445187521 in words is "twenty-one billion, four hundred forty-five million, one hundred eighty-seven thousand, five hundred twenty-one".