20405081 has 2 divisors, whose sum is σ = 20405082. Its totient is φ = 20405080.

The previous prime is 20405059. The next prime is 20405089. The reversal of 20405081 is 18050402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 379456 = 4475^2 + 616^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20405081 is a prime.

It is a super-2 number, since 2×20405081² = 832734661233122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20405089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10202540 + 10202541.

It is an arithmetic number, because the mean of its divisors is an integer number (10202541).

Almost surely, 2^20405081 is an apocalyptic number.

It is an amenable number.

20405081 is a deficient number, since it is larger than the sum of its proper divisors (1).

20405081 is an equidigital number, since it uses as much as digits as its factorization.

20405081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 20405081 is about 4517.1983573892. The cubic root of 20405081 is about 273.2621248506.

Adding to 20405081 its reverse (18050402), we get a palindrome (38455483).

The spelling of 20405081 in words is "twenty million, four hundred five thousand, eighty-one".