16509523781 has 2 divisors, whose sum is σ = 16509523782. Its totient is φ = 16509523780.

The previous prime is 16509523703. The next prime is 16509523799. The reversal of 16509523781 is 18732590561.

16509523781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16162036900 + 347486881 = 127130^2 + 18641^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16509523781 is a prime.

It is a super-2 number, since 2×16509523781² (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 (16509523081) 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, 8254761890 + 8254761891.

It is an arithmetic number, because the mean of its divisors is an integer number (8254761891).

Almost surely, 2^16509523781 is an apocalyptic number.

It is an amenable number.

16509523781 is a deficient number, since it is larger than the sum of its proper divisors (1).

16509523781 is an equidigital number, since it uses as much as digits as its factorization.

16509523781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 453600, while the sum is 47.

The spelling of 16509523781 in words is "sixteen billion, five hundred nine million, five hundred twenty-three thousand, seven hundred eighty-one".