20184991 has 4 divisors (see below), whose sum is σ = 20201184. Its totient is φ = 20168800.

The previous prime is 20184977. The next prime is 20185003. The reversal of 20184991 is 19948102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19948102 = 2 ⋅9974051.

It is a cyclic number.

It is not a de Polignac number, because 20184991 - 2⁵ = 20184959 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 (20184911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6055 + ... + 8776.

It is an arithmetic number, because the mean of its divisors is an integer number (5050296).

Almost surely, 2^20184991 is an apocalyptic number.

20184991 is a deficient number, since it is larger than the sum of its proper divisors (16193).

20184991 is a wasteful number, since it uses less digits than its factorization.

20184991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16192.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 20184991 is about 4492.7709712381. The cubic root of 20184991 is about 272.2760992225.

The spelling of 20184991 in words is "twenty million, one hundred eighty-four thousand, nine hundred ninety-one".