166657781281 has 2 divisors, whose sum is σ = 166657781282. Its totient is φ = 166657781280.

The previous prime is 166657781243. The next prime is 166657781309. The reversal of 166657781281 is 182187756661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 91188900625 + 75468880656 = 301975^2 + 274716^2 .

It is a cyclic number.

It is not a de Polignac number, because 166657781281 - 2⁹ = 166657780769 is a prime.

It is a super-2 number, since 2×166657781281² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (166657781221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83328890640 + 83328890641.

It is an arithmetic number, because the mean of its divisors is an integer number (83328890641).

Almost surely, 2^166657781281 is an apocalyptic number.

It is an amenable number.

166657781281 is a deficient number, since it is larger than the sum of its proper divisors (1).

166657781281 is an equidigital number, since it uses as much as digits as its factorization.

166657781281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6773760, while the sum is 58.

The spelling of 166657781281 in words is "one hundred sixty-six billion, six hundred fifty-seven million, seven hundred eighty-one thousand, two hundred eighty-one".