16646207581 has 2 divisors, whose sum is σ = 16646207582. Its totient is φ = 16646207580.

The previous prime is 16646207573. The next prime is 16646207621. The reversal of 16646207581 is 18570264661.

16646207581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16623976356 + 22231225 = 128934^2 + 4715^2 .

It is a cyclic number.

It is not a de Polignac number, because 16646207581 - 2³ = 16646207573 is a prime.

It is a super-2 number, since 2×16646207581² (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 (16641207581) 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, 8323103790 + 8323103791.

It is an arithmetic number, because the mean of its divisors is an integer number (8323103791).

Almost surely, 2^16646207581 is an apocalyptic number.

It is an amenable number.

16646207581 is a deficient number, since it is larger than the sum of its proper divisors (1).

16646207581 is an equidigital number, since it uses as much as digits as its factorization.

16646207581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 483840, while the sum is 46.

The spelling of 16646207581 in words is "sixteen billion, six hundred forty-six million, two hundred seven thousand, five hundred eighty-one".