666634139581 has 2 divisors, whose sum is σ = 666634139582. Its totient is φ = 666634139580.

The previous prime is 666634139557. The next prime is 666634139599. The reversal of 666634139581 is 185931436666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 358286044900 + 308348094681 = 598570^2 + 555291^2 .

It is a cyclic number.

It is not a de Polignac number, because 666634139581 - 2³⁷ = 529195186109 is a prime.

It is a super-2 number, since 2×666634139581² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666634139531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333317069790 + 333317069791.

It is an arithmetic number, because the mean of its divisors is an integer number (333317069791).

Almost surely, 2^666634139581 is an apocalyptic number.

It is an amenable number.

666634139581 is a deficient number, since it is larger than the sum of its proper divisors (1).

666634139581 is an equidigital number, since it uses as much as digits as its factorization.

666634139581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16796160, while the sum is 58.

The spelling of 666634139581 in words is "six hundred sixty-six billion, six hundred thirty-four million, one hundred thirty-nine thousand, five hundred eighty-one".