21138563 has 2 divisors, whose sum is σ = 21138564. Its totient is φ = 21138562.

The previous prime is 21138547. The next prime is 21138577. The reversal of 21138563 is 36583112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21138563 - 2⁴ = 21138547 is a prime.

It is not a weakly prime, because it can be changed into another prime (21138503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569281 + 10569282.

It is an arithmetic number, because the mean of its divisors is an integer number (10569282).

Almost surely, 2^21138563 is an apocalyptic number.

21138563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138563 is an equidigital number, since it uses as much as digits as its factorization.

21138563 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 21138563 is about 4597.6693008523. The cubic root of 21138563 is about 276.4978891892.

The spelling of 21138563 in words is "twenty-one million, one hundred thirty-eight thousand, five hundred sixty-three".