20837981 has 2 divisors, whose sum is σ = 20837982. Its totient is φ = 20837980.

The previous prime is 20837899. The next prime is 20838011. The reversal of 20837981 is 18973802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16532356 + 4305625 = 4066^2 + 2075^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20837981 is a prime.

It is a super-2 number, since 2×20837981² = 868442904312722, 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 (20837081) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10418990 + 10418991.

It is an arithmetic number, because the mean of its divisors is an integer number (10418991).

Almost surely, 2^20837981 is an apocalyptic number.

It is an amenable number.

20837981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20837981 is an equidigital number, since it uses as much as digits as its factorization.

20837981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 20837981 is about 4564.8637438592. The cubic root of 20837981 is about 275.1810642294.

The spelling of 20837981 in words is "twenty million, eight hundred thirty-seven thousand, nine hundred eighty-one".