21045647417 has 2 divisors, whose sum is σ = 21045647418. Its totient is φ = 21045647416.

The previous prime is 21045647387. The next prime is 21045647453. The reversal of 21045647417 is 71474654012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14099425081 + 6946222336 = 118741^2 + 83344^2 .

It is a cyclic number.

It is not a de Polignac number, because 21045647417 - 2⁶ = 21045647353 is a prime.

It is not a weakly prime, because it can be changed into another prime (21045647317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10522823708 + 10522823709.

It is an arithmetic number, because the mean of its divisors is an integer number (10522823709).

Almost surely, 2^21045647417 is an apocalyptic number.

It is an amenable number.

21045647417 is a deficient number, since it is larger than the sum of its proper divisors (1).

21045647417 is an equidigital number, since it uses as much as digits as its factorization.

21045647417 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 188160, while the sum is 41.

The spelling of 21045647417 in words is "twenty-one billion, forty-five million, six hundred forty-seven thousand, four hundred seventeen".