21082021 has 2 divisors, whose sum is σ = 21082022. Its totient is φ = 21082020.

The previous prime is 21082013. The next prime is 21082063. The reversal of 21082021 is 12028012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21031396 + 50625 = 4586^2 + 225^2 .

It is a cyclic number.

It is not a de Polignac number, because 21082021 - 2³ = 21082013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21081986 and 21082004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21080021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10541010 + 10541011.

It is an arithmetic number, because the mean of its divisors is an integer number (10541011).

Almost surely, 2^21082021 is an apocalyptic number.

It is an amenable number.

21082021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21082021 is an equidigital number, since it uses as much as digits as its factorization.

21082021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 21082021 is about 4591.5161983815. The cubic root of 21082021 is about 276.2511410448.

The spelling of 21082021 in words is "twenty-one million, eighty-two thousand, twenty-one".