20199991 has 4 divisors (see below), whose sum is σ = 23085712. Its totient is φ = 17314272.

The previous prime is 20199973. The next prime is 20200013. The reversal of 20199991 is 19999102.

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 20199991 - 2¹³ = 20191799 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 (20199901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1442850 + ... + 1442863.

It is an arithmetic number, because the mean of its divisors is an integer number (5771428).

Almost surely, 2^20199991 is an apocalyptic number.

20199991 is a deficient number, since it is larger than the sum of its proper divisors (2885721).

20199991 is an equidigital number, since it uses as much as digits as its factorization.

20199991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2885720.

The product of its (nonzero) digits is 13122, while the sum is 40.

The square root of 20199991 is about 4494.4400096119. The cubic root of 20199991 is about 272.3435277098.

The spelling of 20199991 in words is "twenty million, one hundred ninety-nine thousand, nine hundred ninety-one".