67781601821 has 2 divisors, whose sum is σ = 67781601822. Its totient is φ = 67781601820.

The previous prime is 67781601779. The next prime is 67781601829. The reversal of 67781601821 is 12810618776.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 36660760900 + 31120840921 = 191470^2 + 176411^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67781601821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (67781601829) 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, 33890800910 + 33890800911.

It is an arithmetic number, because the mean of its divisors is an integer number (33890800911).

Almost surely, 2^67781601821 is an apocalyptic number.

It is an amenable number.

67781601821 is a deficient number, since it is larger than the sum of its proper divisors (1).

67781601821 is an equidigital number, since it uses as much as digits as its factorization.

67781601821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 225792, while the sum is 47.

The spelling of 67781601821 in words is "sixty-seven billion, seven hundred eighty-one million, six hundred one thousand, eight hundred twenty-one".