20019581 has 2 divisors, whose sum is σ = 20019582. Its totient is φ = 20019580.

The previous prime is 20019577. The next prime is 20019589. The reversal of 20019581 is 18591002.

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., 19882681 + 136900 = 4459^2 + 370^2 .

It is a cyclic number.

It is not a de Polignac number, because 20019581 - 2² = 20019577 is a prime.

It is a super-2 number, since 2×20019581² = 801567246831122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20019581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20019589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10009790 + 10009791.

It is an arithmetic number, because the mean of its divisors is an integer number (10009791).

Almost surely, 2^20019581 is an apocalyptic number.

It is an amenable number.

20019581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20019581 is an equidigital number, since it uses as much as digits as its factorization.

20019581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 20019581 is about 4474.3246417756. The cubic root of 20019581 is about 271.5303177844.

The spelling of 20019581 in words is "twenty million, nineteen thousand, five hundred eighty-one".