67720781 has 2 divisors, whose sum is σ = 67720782. Its totient is φ = 67720780.

The previous prime is 67720753. The next prime is 67720811. The reversal of 67720781 is 18702776.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50836900 + 16883881 = 7130^2 + 4109^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67720781 is a prime.

It is a super-2 number, since 2×67720781² = 9172208358499922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (67720711) 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, 33860390 + 33860391.

It is an arithmetic number, because the mean of its divisors is an integer number (33860391).

Almost surely, 2^67720781 is an apocalyptic number.

It is an amenable number.

67720781 is a deficient number, since it is larger than the sum of its proper divisors (1).

67720781 is an equidigital number, since it uses as much as digits as its factorization.

67720781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32928, while the sum is 38.

The square root of 67720781 is about 8229.2636973182. The cubic root of 67720781 is about 407.6060792498.

The spelling of 67720781 in words is "sixty-seven million, seven hundred twenty thousand, seven hundred eighty-one".