866557421 has 2 divisors, whose sum is σ = 866557422. Its totient is φ = 866557420.

The previous prime is 866557403. The next prime is 866557429. The reversal of 866557421 is 124755668.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 813048196 + 53509225 = 28514^2 + 7315^2 .

It is a cyclic number.

It is not a de Polignac number, because 866557421 - 2²⁶ = 799448557 is a prime.

It is a Sophie Germain prime.

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 (866557429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433278710 + 433278711.

It is an arithmetic number, because the mean of its divisors is an integer number (433278711).

Almost surely, 2^866557421 is an apocalyptic number.

It is an amenable number.

866557421 is a deficient number, since it is larger than the sum of its proper divisors (1).

866557421 is an equidigital number, since it uses as much as digits as its factorization.

866557421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 403200, while the sum is 44.

The square root of 866557421 is about 29437.3473838931. The cubic root of 866557421 is about 953.3794399460.

The spelling of 866557421 in words is "eight hundred sixty-six million, five hundred fifty-seven thousand, four hundred twenty-one".