21540563 has 4 divisors (see below), whose sum is σ = 23498808. Its totient is φ = 19582320.

The previous prime is 21540553. The next prime is 21540583. The reversal of 21540563 is 36504512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21540563 - 2⁸ = 21540307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21540553) 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 in 3 ways as a sum of consecutive naturals, for example, 979106 + ... + 979127.

It is an arithmetic number, because the mean of its divisors is an integer number (5874702).

Almost surely, 2^21540563 is an apocalyptic number.

21540563 is a deficient number, since it is larger than the sum of its proper divisors (1958245).

21540563 is a wasteful number, since it uses less digits than its factorization.

21540563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1958244.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21540563 is about 4641.1812074083. The cubic root of 21540563 is about 278.2396489496.

The spelling of 21540563 in words is "twenty-one million, five hundred forty thousand, five hundred sixty-three".