21605063 has 2 divisors, whose sum is σ = 21605064. Its totient is φ = 21605062.

The previous prime is 21605057. The next prime is 21605081. The reversal of 21605063 is 36050612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21605063 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802531 + 10802532.

It is an arithmetic number, because the mean of its divisors is an integer number (10802532).

Almost surely, 2^21605063 is an apocalyptic number.

21605063 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605063 is an equidigital number, since it uses as much as digits as its factorization.

21605063 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 21605063 is about 4648.1246756084. The cubic root of 21605063 is about 278.5170879134.

Adding to 21605063 its reverse (36050612), we get a palindrome (57655675).

The spelling of 21605063 in words is "twenty-one million, six hundred five thousand, sixty-three".