16680636781 has 2 divisors, whose sum is σ = 16680636782. Its totient is φ = 16680636780.

The previous prime is 16680636773. The next prime is 16680636871. The reversal of 16680636781 is 18763608661.

Together with next prime (16680636871) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13355269225 + 3325367556 = 115565^2 + 57666^2 .

It is a cyclic number.

It is not a de Polignac number, because 16680636781 - 2³ = 16680636773 is a prime.

It is a super-2 number, since 2×16680636781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16680636761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8340318390 + 8340318391.

It is an arithmetic number, because the mean of its divisors is an integer number (8340318391).

Almost surely, 2^16680636781 is an apocalyptic number.

It is an amenable number.

16680636781 is a deficient number, since it is larger than the sum of its proper divisors (1).

16680636781 is an equidigital number, since it uses as much as digits as its factorization.

16680636781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1741824, while the sum is 52.

The spelling of 16680636781 in words is "sixteen billion, six hundred eighty million, six hundred thirty-six thousand, seven hundred eighty-one".