21005309473 has 2 divisors, whose sum is σ = 21005309474. Its totient is φ = 21005309472.

The previous prime is 21005309453. The next prime is 21005309483. The reversal of 21005309473 is 37490350012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20999777569 + 5531904 = 144913^2 + 2352^2 .

It is a cyclic number.

It is not a de Polignac number, because 21005309473 - 2¹³ = 21005301281 is a prime.

It is not a weakly prime, because it can be changed into another prime (21005309443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502654736 + 10502654737.

It is an arithmetic number, because the mean of its divisors is an integer number (10502654737).

Almost surely, 2^21005309473 is an apocalyptic number.

It is an amenable number.

21005309473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005309473 is an equidigital number, since it uses as much as digits as its factorization.

21005309473 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 22680, while the sum is 34.

Adding to 21005309473 its reverse (37490350012), we get a palindrome (58495659485).

The spelling of 21005309473 in words is "twenty-one billion, five million, three hundred nine thousand, four hundred seventy-three".