16561399 has 2 divisors, whose sum is σ = 16561400. Its totient is φ = 16561398.

The previous prime is 16561397. The next prime is 16561411. The reversal of 16561399 is 99316561.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 16561399 - 2¹ = 16561397 is a prime.

Together with 16561397, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16561397) 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, 8280699 + 8280700.

It is an arithmetic number, because the mean of its divisors is an integer number (8280700).

Almost surely, 2^16561399 is an apocalyptic number.

16561399 is a deficient number, since it is larger than the sum of its proper divisors (1).

16561399 is an equidigital number, since it uses as much as digits as its factorization.

16561399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43740, while the sum is 40.

The square root of 16561399 is about 4069.5698789921. The cubic root of 16561399 is about 254.8975572101.

The spelling of 16561399 in words is "sixteen million, five hundred sixty-one thousand, three hundred ninety-nine".