661181977 has 2 divisors, whose sum is σ = 661181978. Its totient is φ = 661181976.

The previous prime is 661181923. The next prime is 661181993. The reversal of 661181977 is 779181166.

661181977 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 576192016 + 84989961 = 24004^2 + 9219^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661181977 is a prime.

It is not a weakly prime, because it can be changed into another prime (661181077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330590988 + 330590989.

It is an arithmetic number, because the mean of its divisors is an integer number (330590989).

Almost surely, 2^661181977 is an apocalyptic number.

It is an amenable number.

661181977 is a deficient number, since it is larger than the sum of its proper divisors (1).

661181977 is an equidigital number, since it uses as much as digits as its factorization.

661181977 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 127008, while the sum is 46.

The square root of 661181977 is about 25713.4590632999. The cubic root of 661181977 is about 871.1782059465.

It can be divided in two parts, 6611 and 81977, that added together give a palindrome (88588).

The spelling of 661181977 in words is "six hundred sixty-one million, one hundred eighty-one thousand, nine hundred seventy-seven".