21643117 has 2 divisors, whose sum is σ = 21643118. Its totient is φ = 21643116.

The previous prime is 21643103. The next prime is 21643129. The reversal of 21643117 is 71134612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16232841 + 5410276 = 4029^2 + 2326^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643117 - 2¹⁹ = 21118829 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21643091 and 21643100.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21643217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821558 + 10821559.

It is an arithmetic number, because the mean of its divisors is an integer number (10821559).

Almost surely, 2^21643117 is an apocalyptic number.

It is an amenable number.

21643117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21643117 is an equidigital number, since it uses as much as digits as its factorization.

21643117 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 25.

The square root of 21643117 is about 4652.2163535244. The cubic root of 21643117 is about 278.6805136914.

Adding to 21643117 its reverse (71134612), we get a palindrome (92777729).

The spelling of 21643117 in words is "twenty-one million, six hundred forty-three thousand, one hundred seventeen".