21382121 has 2 divisors, whose sum is σ = 21382122. Its totient is φ = 21382120.

The previous prime is 21382103. The next prime is 21382129. The reversal of 21382121 is 12128312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18705625 + 2676496 = 4325^2 + 1636^2 .

It is a cyclic number.

It is not a de Polignac number, because 21382121 - 2⁶ = 21382057 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21382093 and 21382102.

It is not a weakly prime, because it can be changed into another prime (21382129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10691060 + 10691061.

It is an arithmetic number, because the mean of its divisors is an integer number (10691061).

Almost surely, 2^21382121 is an apocalyptic number.

It is an amenable number.

21382121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21382121 is an equidigital number, since it uses as much as digits as its factorization.

21382121 is an evil number, because the sum of its binary digits is even.

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

The square root of 21382121 is about 4624.0805572568. The cubic root of 21382121 is about 277.5557705185. Note that the first 3 decimals are identical.

The spelling of 21382121 in words is "twenty-one million, three hundred eighty-two thousand, one hundred twenty-one".