2021906581 has 2 divisors, whose sum is σ = 2021906582. Its totient is φ = 2021906580.

The previous prime is 2021906573. The next prime is 2021906587. The reversal of 2021906581 is 1856091202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2016459025 + 5447556 = 44905^2 + 2334^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021906581 - 2³ = 2021906573 is a prime.

It is a super-2 number, since 2×2021906581² = 8176212444582219122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2021906587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1010953290 + 1010953291.

It is an arithmetic number, because the mean of its divisors is an integer number (1010953291).

Almost surely, 2^2021906581 is an apocalyptic number.

It is an amenable number.

2021906581 is a deficient number, since it is larger than the sum of its proper divisors (1).

2021906581 is an equidigital number, since it uses as much as digits as its factorization.

2021906581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 2021906581 is about 44965.6155412110. The cubic root of 2021906581 is about 1264.5044497249.

Adding to 2021906581 its reverse (1856091202), we get a palindrome (3877997783).

The spelling of 2021906581 in words is "two billion, twenty-one million, nine hundred six thousand, five hundred eighty-one".