20123791 has 4 divisors (see below), whose sum is σ = 20259000. Its totient is φ = 19988584.

The previous prime is 20123783. The next prime is 20123809. The reversal of 20123791 is 19732102.

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 20123791 - 2³ = 20123783 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 (20123771) 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 3 ways as a sum of consecutive naturals, for example, 67381 + ... + 67678.

It is an arithmetic number, because the mean of its divisors is an integer number (5064750).

Almost surely, 2^20123791 is an apocalyptic number.

20123791 is a deficient number, since it is larger than the sum of its proper divisors (135209).

20123791 is a wasteful number, since it uses less digits than its factorization.

20123791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135208.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 20123791 is about 4485.9548593360. The cubic root of 20123791 is about 272.0006442819. Note that the first 3 decimals are identical.

Adding to 20123791 its reverse (19732102), we get a palindrome (39855893).

The spelling of 20123791 in words is "twenty million, one hundred twenty-three thousand, seven hundred ninety-one".