266539791821 has 2 divisors, whose sum is σ = 266539791822. Its totient is φ = 266539791820.

The previous prime is 266539791803. The next prime is 266539791827. The reversal of 266539791821 is 128197935662.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 181983294025 + 84556497796 = 426595^2 + 290786^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-266539791821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (266539791827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 133269895910 + 133269895911.

It is an arithmetic number, because the mean of its divisors is an integer number (133269895911).

Almost surely, 2^266539791821 is an apocalyptic number.

It is an amenable number.

266539791821 is a deficient number, since it is larger than the sum of its proper divisors (1).

266539791821 is an equidigital number, since it uses as much as digits as its factorization.

266539791821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9797760, while the sum is 59.

The spelling of 266539791821 in words is "two hundred sixty-six billion, five hundred thirty-nine million, seven hundred ninety-one thousand, eight hundred twenty-one".