81826021 has 2 divisors, whose sum is σ = 81826022. Its totient is φ = 81826020.

The previous prime is 81825983. The next prime is 81826057. The reversal of 81826021 is 12062818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81703521 + 122500 = 9039^2 + 350^2 .

It is a cyclic number.

It is not a de Polignac number, because 81826021 - 2⁷ = 81825893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81826621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40913010 + 40913011.

It is an arithmetic number, because the mean of its divisors is an integer number (40913011).

Almost surely, 2^81826021 is an apocalyptic number.

It is an amenable number.

81826021 is a deficient number, since it is larger than the sum of its proper divisors (1).

81826021 is an equidigital number, since it uses as much as digits as its factorization.

81826021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 81826021 is about 9045.7736540331. The cubic root of 81826021 is about 434.1406755137.

Adding to 81826021 its reverse (12062818), we get a palindrome (93888839).

The spelling of 81826021 in words is "eighty-one million, eight hundred twenty-six thousand, twenty-one".