20805871 has 2 divisors, whose sum is σ = 20805872. Its totient is φ = 20805870.

The previous prime is 20805853. The next prime is 20805887. The reversal of 20805871 is 17850802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20805871 - 2¹¹ = 20803823 is a prime.

It is equal to p_1318468 and since 20805871 and 1318468 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20805571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10402935 + 10402936.

It is an arithmetic number, because the mean of its divisors is an integer number (10402936).

Almost surely, 2^20805871 is an apocalyptic number.

20805871 is a deficient number, since it is larger than the sum of its proper divisors (1).

20805871 is an equidigital number, since it uses as much as digits as its factorization.

20805871 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4480, while the sum is 31.

The square root of 20805871 is about 4561.3453059377. The cubic root of 20805871 is about 275.0396460747.

The spelling of 20805871 in words is "twenty million, eight hundred five thousand, eight hundred seventy-one".