20841581 has 2 divisors, whose sum is σ = 20841582. Its totient is φ = 20841580.

The previous prime is 20841577. The next prime is 20841629. The reversal of 20841581 is 18514802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20620681 + 220900 = 4541^2 + 470^2 .

It is a cyclic number.

It is not a de Polignac number, because 20841581 - 2² = 20841577 is a prime.

It is a super-2 number, since 2×20841581² = 868742997159122, 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 (20841181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10420790 + 10420791.

It is an arithmetic number, because the mean of its divisors is an integer number (10420791).

Almost surely, 2^20841581 is an apocalyptic number.

It is an amenable number.

20841581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20841581 is an equidigital number, since it uses as much as digits as its factorization.

20841581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2560, while the sum is 29.

The square root of 20841581 is about 4565.2580430902. The cubic root of 20841581 is about 275.1969102110.

The spelling of 20841581 in words is "twenty million, eight hundred forty-one thousand, five hundred eighty-one".