77431681321 has 2 divisors, whose sum is σ = 77431681322. Its totient is φ = 77431681320.

The previous prime is 77431681319. The next prime is 77431681339. The reversal of 77431681321 is 12318613477.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 60703104400 + 16728576921 = 246380^2 + 129339^2 .

It is an emirp because it is prime and its reverse (12318613477) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77431681321 - 2¹ = 77431681319 is a prime.

Together with 77431681319, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (77431681351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38715840660 + 38715840661.

It is an arithmetic number, because the mean of its divisors is an integer number (38715840661).

Almost surely, 2^77431681321 is an apocalyptic number.

It is an amenable number.

77431681321 is a deficient number, since it is larger than the sum of its proper divisors (1).

77431681321 is an equidigital number, since it uses as much as digits as its factorization.

77431681321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 169344, while the sum is 43.

The spelling of 77431681321 in words is "seventy-seven billion, four hundred thirty-one million, six hundred eighty-one thousand, three hundred twenty-one".