67777777777781 has 2 divisors, whose sum is σ = 67777777777782. Its totient is φ = 67777777777780.

The previous prime is 67777777777777. The next prime is 67777777777793. The reversal of 67777777777781 is 18777777777776.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67189743394225 + 588034383556 = 8196935^2 + 766834^2 .

It is a cyclic number.

It is not a de Polignac number, because 67777777777781 - 2² = 67777777777777 is a prime.

It is a super-2 number, since 2×67777777777781² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (67777777777711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33888888888890 + 33888888888891.

It is an arithmetic number, because the mean of its divisors is an integer number (33888888888891).

Almost surely, 2^{67777777777781} is an apocalyptic number.

It is an amenable number.

67777777777781 is a deficient number, since it is larger than the sum of its proper divisors (1).

67777777777781 is an equidigital number, since it uses as much as digits as its factorization.

67777777777781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 94911683664, while the sum is 92.

The spelling of 67777777777781 in words is "sixty-seven trillion, seven hundred seventy-seven billion, seven hundred seventy-seven million, seven hundred seventy-seven thousand, seven hundred eighty-one".