21026081 has 2 divisors, whose sum is σ = 21026082. Its totient is φ = 21026080.

The previous prime is 21026069. The next prime is 21026099. The reversal of 21026081 is 18062012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 2835856 = 4265^2 + 1684^2 .

It is a cyclic number.

It is not a de Polignac number, because 21026081 - 2¹⁴ = 21009697 is a prime.

It is a super-2 number, since 2×21026081² = 884192164437122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21026381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513040 + 10513041.

It is an arithmetic number, because the mean of its divisors is an integer number (10513041).

Almost surely, 2^21026081 is an apocalyptic number.

It is an amenable number.

21026081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026081 is an equidigital number, since it uses as much as digits as its factorization.

21026081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21026081 is about 4585.4204823549. The cubic root of 21026081 is about 276.0065854691.

Adding to 21026081 its reverse (18062012), we get a palindrome (39088093).

The spelling of 21026081 in words is "twenty-one million, twenty-six thousand, eighty-one".