16991623 has 4 divisors (see below), whose sum is σ = 18536328. Its totient is φ = 15446920.

The previous prime is 16991599. The next prime is 16991629. The reversal of 16991623 is 32619961.

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 16991623 - 2⁵ = 16991591 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16991629) 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, 772336 + ... + 772357.

It is an arithmetic number, because the mean of its divisors is an integer number (4634082).

Almost surely, 2^16991623 is an apocalyptic number.

16991623 is a deficient number, since it is larger than the sum of its proper divisors (1544705).

16991623 is a wasteful number, since it uses less digits than its factorization.

16991623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1544704.

The product of its digits is 17496, while the sum is 37.

The square root of 16991623 is about 4122.0896399763. The cubic root of 16991623 is about 257.0859175661.

The spelling of 16991623 in words is "sixteen million, nine hundred ninety-one thousand, six hundred twenty-three".