21566873 has 2 divisors, whose sum is σ = 21566874. Its totient is φ = 21566872.

The previous prime is 21566837. The next prime is 21566887. The reversal of 21566873 is 37866512.

Together with previous prime (21566837) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11751184 + 9815689 = 3428^2 + 3133^2 .

It is a cyclic number.

It is not a de Polignac number, because 21566873 - 2¹⁰ = 21565849 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 (21566473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10783436 + 10783437.

It is an arithmetic number, because the mean of its divisors is an integer number (10783437).

Almost surely, 2^21566873 is an apocalyptic number.

It is an amenable number.

21566873 is a deficient number, since it is larger than the sum of its proper divisors (1).

21566873 is an equidigital number, since it uses as much as digits as its factorization.

21566873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 38.

The square root of 21566873 is about 4644.0147501919. The cubic root of 21566873 is about 278.3528850294.

The spelling of 21566873 in words is "twenty-one million, five hundred sixty-six thousand, eight hundred seventy-three".