21390041 has 2 divisors, whose sum is σ = 21390042. Its totient is φ = 21390040.

The previous prime is 21390011. The next prime is 21390043. The reversal of 21390041 is 14009312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 4084441 = 4160^2 + 2021^2 .

It is a cyclic number.

It is not a de Polignac number, because 21390041 - 2¹⁴ = 21373657 is a prime.

It is a Sophie Germain prime.

Together with 21390043, it forms a pair of twin primes.

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 = 21389995 and 21390022.

It is not a weakly prime, because it can be changed into another prime (21390043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695020 + 10695021.

It is an arithmetic number, because the mean of its divisors is an integer number (10695021).

Almost surely, 2^21390041 is an apocalyptic number.

It is an amenable number.

21390041 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390041 is an equidigital number, since it uses as much as digits as its factorization.

21390041 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21390041 is about 4624.9368644339. The cubic root of 21390041 is about 277.5900354439.

Adding to 21390041 its reverse (14009312), we get a palindrome (35399353).

The spelling of 21390041 in words is "twenty-one million, three hundred ninety thousand, forty-one".