20875781 has 2 divisors, whose sum is σ = 20875782. Its totient is φ = 20875780.

The previous prime is 20875759. The next prime is 20875817. The reversal of 20875781 is 18757802.

Together with next prime (20875817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11628100 + 9247681 = 3410^2 + 3041^2 .

It is a cyclic number.

It is not a de Polignac number, because 20875781 - 2²² = 16681477 is a prime.

It is a super-2 number, since 2×20875781² = 871596464719922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20875721) 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 as a sum of consecutive naturals, namely, 10437890 + 10437891.

It is an arithmetic number, because the mean of its divisors is an integer number (10437891).

Almost surely, 2^20875781 is an apocalyptic number.

It is an amenable number.

20875781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20875781 is an equidigital number, since it uses as much as digits as its factorization.

20875781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31360, while the sum is 38.

The square root of 20875781 is about 4569.0021886622. The cubic root of 20875781 is about 275.3473561065.

The spelling of 20875781 in words is "twenty million, eight hundred seventy-five thousand, seven hundred eighty-one".