255566021 has 2 divisors, whose sum is σ = 255566022. Its totient is φ = 255566020.

The previous prime is 255565963. The next prime is 255566023. The reversal of 255566021 is 120665552.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 255520225 + 45796 = 15985^2 + 214^2 .

It is a cyclic number.

It is not a de Polignac number, because 255566021 - 2⁶ = 255565957 is a prime.

It is a Sophie Germain prime.

Together with 255566023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (255566023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 127783010 + 127783011.

It is an arithmetic number, because the mean of its divisors is an integer number (127783011).

Almost surely, 2^255566021 is an apocalyptic number.

It is an amenable number.

255566021 is a deficient number, since it is larger than the sum of its proper divisors (1).

255566021 is an equidigital number, since it uses as much as digits as its factorization.

255566021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18000, while the sum is 32.

The square root of 255566021 is about 15986.4324037604. The cubic root of 255566021 is about 634.6014164285.

The spelling of 255566021 in words is "two hundred fifty-five million, five hundred sixty-six thousand, twenty-one".