21068221 has 2 divisors, whose sum is σ = 21068222. Its totient is φ = 21068220.

The previous prime is 21068213. The next prime is 21068227. The reversal of 21068221 is 12286012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 121 = 4590^2 + 11^2 .

It is a cyclic number.

It is not a de Polignac number, because 21068221 - 2³ = 21068213 is a prime.

It is a super-2 number, since 2×21068221² = 887739872209682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21068192 and 21068201.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21068227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10534110 + 10534111.

It is an arithmetic number, because the mean of its divisors is an integer number (10534111).

Almost surely, 2^21068221 is an apocalyptic number.

It is an amenable number.

21068221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21068221 is an equidigital number, since it uses as much as digits as its factorization.

21068221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21068221 is about 4590.0131808090. The cubic root of 21068221 is about 276.1908511598.

The spelling of 21068221 in words is "twenty-one million, sixty-eight thousand, two hundred twenty-one".