21166559 has 2 divisors, whose sum is σ = 21166560. Its totient is φ = 21166558.

The previous prime is 21166529. The next prime is 21166567. The reversal of 21166559 is 95566112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21166559 - 2⁸ = 21166303 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21166529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10583279 + 10583280.

It is an arithmetic number, because the mean of its divisors is an integer number (10583280).

Almost surely, 2^21166559 is an apocalyptic number.

21166559 is a deficient number, since it is larger than the sum of its proper divisors (1).

21166559 is an equidigital number, since it uses as much as digits as its factorization.

21166559 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16200, while the sum is 35.

The square root of 21166559 is about 4600.7128795438. The cubic root of 21166559 is about 276.6199003226.

The spelling of 21166559 in words is "twenty-one million, one hundred sixty-six thousand, five hundred fifty-nine".