766661155781 has 2 divisors, whose sum is σ = 766661155782. Its totient is φ = 766661155780.

The previous prime is 766661155769. The next prime is 766661155789. The reversal of 766661155781 is 187551166667.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 715265998756 + 51395157025 = 845734^2 + 226705^2 .

It is a cyclic number.

It is not a de Polignac number, because 766661155781 - 2²⁶ = 766594046917 is a prime.

It is a super-2 number, since 2×766661155781² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 766661155781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (766661155789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 383330577890 + 383330577891.

It is an arithmetic number, because the mean of its divisors is an integer number (383330577891).

Almost surely, 2^766661155781 is an apocalyptic number.

It is an amenable number.

766661155781 is a deficient number, since it is larger than the sum of its proper divisors (1).

766661155781 is an equidigital number, since it uses as much as digits as its factorization.

766661155781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12700800, while the sum is 59.

The spelling of 766661155781 in words is "seven hundred sixty-six billion, six hundred sixty-one million, one hundred fifty-five thousand, seven hundred eighty-one".