866123857473821 has 2 divisors, whose sum is σ = 866123857473822. Its totient is φ = 866123857473820.

The previous prime is 866123857473737. The next prime is 866123857473859. The reversal of 866123857473821 is 128374758321668.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 509218082671321 + 356905774802500 = 22565861^2 + 18891950^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-866123857473821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866123857473871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433061928736910 + 433061928736911.

It is an arithmetic number, because the mean of its divisors is an integer number (433061928736911).

Almost surely, 2^{866123857473821} is an apocalyptic number.

It is an amenable number.

866123857473821 is a deficient number, since it is larger than the sum of its proper divisors (1).

866123857473821 is an equidigital number, since it uses as much as digits as its factorization.

866123857473821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 650280960, while the sum is 71.

The spelling of 866123857473821 in words is "eight hundred sixty-six trillion, one hundred twenty-three billion, eight hundred fifty-seven million, four hundred seventy-three thousand, eight hundred twenty-one".