16561691 has 2 divisors, whose sum is σ = 16561692. Its totient is φ = 16561690.

The previous prime is 16561669. The next prime is 16561703. The reversal of 16561691 is 19616561.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 16561691 - 2⁶ = 16561627 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16561661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8280845 + 8280846.

It is an arithmetic number, because the mean of its divisors is an integer number (8280846).

Almost surely, 2^16561691 is an apocalyptic number.

16561691 is a deficient number, since it is larger than the sum of its proper divisors (1).

16561691 is an equidigital number, since it uses as much as digits as its factorization.

16561691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9720, while the sum is 35.

The square root of 16561691 is about 4069.6057548613. The cubic root of 16561691 is about 254.8990552649.

The spelling of 16561691 in words is "sixteen million, five hundred sixty-one thousand, six hundred ninety-one".