20517823 has 2 divisors, whose sum is σ = 20517824. Its totient is φ = 20517822.

The previous prime is 20517821. The next prime is 20517829. The reversal of 20517823 is 32871502.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20517823 - 2¹ = 20517821 is a prime.

Together with 20517821, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 20517791 and 20517800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20517821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10258911 + 10258912.

It is an arithmetic number, because the mean of its divisors is an integer number (10258912).

Almost surely, 2^20517823 is an apocalyptic number.

20517823 is a deficient number, since it is larger than the sum of its proper divisors (1).

20517823 is an equidigital number, since it uses as much as digits as its factorization.

20517823 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 20517823 is about 4529.6603625438. The cubic root of 20517823 is about 273.7644760664.

The spelling of 20517823 in words is "twenty million, five hundred seventeen thousand, eight hundred twenty-three".