67878781 has 2 divisors, whose sum is σ = 67878782. Its totient is φ = 67878780.

The previous prime is 67878779. The next prime is 67878791. The reversal of 67878781 is 18787876.

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., 43956900 + 23921881 = 6630^2 + 4891^2 .

It is a cyclic number.

It is not a de Polignac number, because 67878781 - 2¹ = 67878779 is a prime.

It is a super-2 number, since 2×67878781² = 9215057820091922, which contains 22 as substring.

Together with 67878779, it forms a pair of twin primes.

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

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (67878731) 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, 33939390 + 33939391.

It is an arithmetic number, because the mean of its divisors is an integer number (33939391).

Almost surely, 2^67878781 is an apocalyptic number.

It is an amenable number.

67878781 is a deficient number, since it is larger than the sum of its proper divisors (1).

67878781 is an equidigital number, since it uses as much as digits as its factorization.

67878781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1053696, while the sum is 52.

The square root of 67878781 is about 8238.8579912510. The cubic root of 67878781 is about 407.9228295832.

It can be divided in two parts, 6 and 7878781, that added together give a palindrome (7878787).

The spelling of 67878781 in words is "sixty-seven million, eight hundred seventy-eight thousand, seven hundred eighty-one".