16991323 has 4 divisors (see below), whose sum is σ = 17311968. Its totient is φ = 16670680.

The previous prime is 16991311. The next prime is 16991327. The reversal of 16991323 is 32319961.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32319961 = 43 ⋅751627.

It is a cyclic number.

It is not a de Polignac number, because 16991323 - 2²¹ = 14894171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16991327) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 160243 + ... + 160348.

It is an arithmetic number, because the mean of its divisors is an integer number (4327992).

Almost surely, 2^16991323 is an apocalyptic number.

16991323 is a deficient number, since it is larger than the sum of its proper divisors (320645).

16991323 is an equidigital number, since it uses as much as digits as its factorization.

16991323 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320644.

The product of its digits is 8748, while the sum is 34.

The square root of 16991323 is about 4122.0532505051. The cubic root of 16991323 is about 257.0844045416.

Adding to 16991323 its product of digits (8748), we get a palindrome (17000071).

The spelling of 16991323 in words is "sixteen million, nine hundred ninety-one thousand, three hundred twenty-three".