20041981 has 2 divisors, whose sum is σ = 20041982. Its totient is φ = 20041980.

The previous prime is 20041969. The next prime is 20042041. The reversal of 20041981 is 18914002.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10176100 + 9865881 = 3190^2 + 3141^2 .

It is a cyclic number.

It is not a de Polignac number, because 20041981 - 2¹¹ = 20039933 is a prime.

It is a super-2 number, since 2×20041981² = 803362004808722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20041921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10020990 + 10020991.

It is an arithmetic number, because the mean of its divisors is an integer number (10020991).

Almost surely, 2^20041981 is an apocalyptic number.

It is an amenable number.

20041981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20041981 is an equidigital number, since it uses as much as digits as its factorization.

20041981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 20041981 is about 4476.8271130344. The cubic root of 20041981 is about 271.6315522047.

Adding to 20041981 its reverse (18914002), we get a palindrome (38955983).

The spelling of 20041981 in words is "twenty million, forty-one thousand, nine hundred eighty-one".