21563471 has 2 divisors, whose sum is σ = 21563472. Its totient is φ = 21563470.

The previous prime is 21563467. The next prime is 21563491. The reversal of 21563471 is 17436512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21563471 - 2² = 21563467 is a prime.

It is a super-3 number, since 3×21563471³ (a number of 23 digits) contains 333 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21563491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10781735 + 10781736.

It is an arithmetic number, because the mean of its divisors is an integer number (10781736).

Almost surely, 2^21563471 is an apocalyptic number.

21563471 is a deficient number, since it is larger than the sum of its proper divisors (1).

21563471 is an equidigital number, since it uses as much as digits as its factorization.

21563471 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 29.

The square root of 21563471 is about 4643.6484578400. The cubic root of 21563471 is about 278.3382482867.

Adding to 21563471 its reverse (17436512), we get a palindrome (38999983).

The spelling of 21563471 in words is "twenty-one million, five hundred sixty-three thousand, four hundred seventy-one".