16991861 has 2 divisors, whose sum is σ = 16991862. Its totient is φ = 16991860.

The previous prime is 16991851. The next prime is 16991867. The reversal of 16991861 is 16819961.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13359025 + 3632836 = 3655^2 + 1906^2 .

It is an emirp because it is prime and its reverse (16819961) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16991861 - 2¹⁴ = 16975477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16991867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8495930 + 8495931.

It is an arithmetic number, because the mean of its divisors is an integer number (8495931).

Almost surely, 2^16991861 is an apocalyptic number.

It is an amenable number.

16991861 is a deficient number, since it is larger than the sum of its proper divisors (1).

16991861 is an equidigital number, since it uses as much as digits as its factorization.

16991861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 41.

The square root of 16991861 is about 4122.1185087282. The cubic root of 16991861 is about 257.0871178863.

The spelling of 16991861 in words is "sixteen million, nine hundred ninety-one thousand, eight hundred sixty-one".