16991691 has 4 divisors (see below), whose sum is σ = 22655592. Its totient is φ = 11327792.

The previous prime is 16991659. The next prime is 16991701. The reversal of 16991691 is 19619961.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 16991691 - 2⁵ = 16991659 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16991591) 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 in 3 ways as a sum of consecutive naturals, for example, 2831946 + ... + 2831951.

It is an arithmetic number, because the mean of its divisors is an integer number (5663898).

Almost surely, 2^16991691 is an apocalyptic number.

16991691 is a deficient number, since it is larger than the sum of its proper divisors (5663901).

16991691 is an equidigital number, since it uses as much as digits as its factorization.

16991691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5663900.

The product of its digits is 26244, while the sum is 42.

The square root of 16991691 is about 4122.0978882118. The cubic root of 16991691 is about 257.0862605159.

The spelling of 16991691 in words is "sixteen million, nine hundred ninety-one thousand, six hundred ninety-one".