78781 has 2 divisors, whose sum is σ = 78782. Its totient is φ = 78780.

The previous prime is 78779. The next prime is 78787. The reversal of 78781 is 18787.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54756 + 24025 = 234^2 + 155^2 .

It is an emirp because it is prime and its reverse (18787) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78781 - 2¹ = 78779 is a prime.

It is a super-2 number, since 2×78781² = 12412891922, which contains 22 as substring.

Together with 78779, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39390 + 39391.

It is an arithmetic number, because the mean of its divisors is an integer number (39391).

2⁷⁸⁷⁸¹ is an apocalyptic number.

It is an amenable number.

78781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78781 is an equidigital number, since it uses as much as digits as its factorization.

78781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3136, while the sum is 31.

The square root of 78781 is about 280.6795325634. The cubic root of 78781 is about 42.8687180374.

It can be divided in two parts, 787 and 81, that added together give a palindrome (868).

The spelling of 78781 in words is "seventy-eight thousand, seven hundred eighty-one".