21563513 has 2 divisors, whose sum is σ = 21563514. Its totient is φ = 21563512.

The previous prime is 21563491. The next prime is 21563519. The reversal of 21563513 is 31536512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18207289 + 3356224 = 4267^2 + 1832^2 .

It is a cyclic number.

It is not a de Polignac number, because 21563513 - 2⁶ = 21563449 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21563519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10781756 + 10781757.

It is an arithmetic number, because the mean of its divisors is an integer number (10781757).

Almost surely, 2^21563513 is an apocalyptic number.

It is an amenable number.

21563513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21563513 is an equidigital number, since it uses as much as digits as its factorization.

21563513 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2700, while the sum is 26.

The square root of 21563513 is about 4643.6529801440. The cubic root of 21563513 is about 278.3384289966.

The spelling of 21563513 in words is "twenty-one million, five hundred sixty-three thousand, five hundred thirteen".