21563413 has 2 divisors, whose sum is σ = 21563414. Its totient is φ = 21563412.

The previous prime is 21563387. The next prime is 21563419. The reversal of 21563413 is 31436512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13712209 + 7851204 = 3703^2 + 2802^2 .

It is a cyclic number.

It is not a de Polignac number, because 21563413 - 2⁹ = 21562901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21563419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10781706 + 10781707.

It is an arithmetic number, because the mean of its divisors is an integer number (10781707).

Almost surely, 2^21563413 is an apocalyptic number.

It is an amenable number.

21563413 is a deficient number, since it is larger than the sum of its proper divisors (1).

21563413 is an equidigital number, since it uses as much as digits as its factorization.

21563413 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 25.

The square root of 21563413 is about 4643.6422127464. The cubic root of 21563413 is about 278.3379987346.

Adding to 21563413 its reverse (31436512), we get a palindrome (52999925).

The spelling of 21563413 in words is "twenty-one million, five hundred sixty-three thousand, four hundred thirteen".