20189991 has 8 divisors (see below), whose sum is σ = 26944384. Its totient is φ = 13447800.

The previous prime is 20189971. The next prime is 20190013. The reversal of 20189991 is 19998102.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20189991 - 2⁶ = 20189927 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 (20189941) 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 7 ways as a sum of consecutive naturals, for example, 2016 + ... + 6666.

It is an arithmetic number, because the mean of its divisors is an integer number (3368048).

Almost surely, 2^20189991 is an apocalyptic number.

20189991 is a deficient number, since it is larger than the sum of its proper divisors (6754393).

20189991 is a wasteful number, since it uses less digits than its factorization.

20189991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6101.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 20189991 is about 4493.3273862473. The cubic root of 20189991 is about 272.2985790955.

The spelling of 20189991 in words is "twenty million, one hundred eighty-nine thousand, nine hundred ninety-one".