21209865792473 has 2 divisors, whose sum is σ = 21209865792474. Its totient is φ = 21209865792472.

The previous prime is 21209865792469. The next prime is 21209865792523. The reversal of 21209865792473 is 37429756890212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20463029337664 + 746836454809 = 4523608^2 + 864197^2 .

It is a cyclic number.

It is not a de Polignac number, because 21209865792473 - 2² = 21209865792469 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21209865792463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604932896236 + 10604932896237.

It is an arithmetic number, because the mean of its divisors is an integer number (10604932896237).

It is a 1-persistent number, because it is pandigital, but 2⋅21209865792473 = 42419731584946 is not.

Almost surely, 2^{21209865792473} is an apocalyptic number.

It is an amenable number.

21209865792473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21209865792473 is an equidigital number, since it uses as much as digits as its factorization.

21209865792473 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 91445760, while the sum is 65.

The spelling of 21209865792473 in words is "twenty-one trillion, two hundred nine billion, eight hundred sixty-five million, seven hundred ninety-two thousand, four hundred seventy-three".