21158563 has 2 divisors, whose sum is σ = 21158564. Its totient is φ = 21158562.

The previous prime is 21158549. The next prime is 21158633. The reversal of 21158563 is 36585112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21158563 - 2⁹ = 21158051 is a prime.

It is not a weakly prime, because it can be changed into another prime (21158063) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10579281 + 10579282.

It is an arithmetic number, because the mean of its divisors is an integer number (10579282).

Almost surely, 2^21158563 is an apocalyptic number.

21158563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21158563 is an equidigital number, since it uses as much as digits as its factorization.

21158563 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 31.

The square root of 21158563 is about 4599.8438016959. The cubic root of 21158563 is about 276.5850634320.

The spelling of 21158563 in words is "twenty-one million, one hundred fifty-eight thousand, five hundred sixty-three".