77813587781 has 2 divisors, whose sum is σ = 77813587782. Its totient is φ = 77813587780.

The previous prime is 77813587763. The next prime is 77813587783. The reversal of 77813587781 is 18778531877.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61487137156 + 16326450625 = 247966^2 + 127775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77813587781 is a prime.

It is a super-2 number, since 2×77813587781² (a number of 23 digits) contains 22 as substring.

Together with 77813587783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77813587783) 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, 38906793890 + 38906793891.

It is an arithmetic number, because the mean of its divisors is an integer number (38906793891).

Almost surely, 2^77813587781 is an apocalyptic number.

It is an amenable number.

77813587781 is a deficient number, since it is larger than the sum of its proper divisors (1).

77813587781 is an equidigital number, since it uses as much as digits as its factorization.

77813587781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18439680, while the sum is 62.

The spelling of 77813587781 in words is "seventy-seven billion, eight hundred thirteen million, five hundred eighty-seven thousand, seven hundred eighty-one".