21306541 has 2 divisors, whose sum is σ = 21306542. Its totient is φ = 21306540.

The previous prime is 21306539. The next prime is 21306547. The reversal of 21306541 is 14560312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12180100 + 9126441 = 3490^2 + 3021^2 .

It is a cyclic number.

It is not a de Polignac number, because 21306541 - 2¹ = 21306539 is a prime.

Together with 21306539, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21306547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653270 + 10653271.

It is an arithmetic number, because the mean of its divisors is an integer number (10653271).

Almost surely, 2^21306541 is an apocalyptic number.

It is an amenable number.

21306541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21306541 is an equidigital number, since it uses as much as digits as its factorization.

21306541 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21306541 is about 4615.9008871508. The cubic root of 21306541 is about 277.2283563114.

Adding to 21306541 its reverse (14560312), we get a palindrome (35866853).

The spelling of 21306541 in words is "twenty-one million, three hundred six thousand, five hundred forty-one".