21540559 has 4 divisors (see below), whose sum is σ = 21551320. Its totient is φ = 21529800.

The previous prime is 21540553. The next prime is 21540583. The reversal of 21540559 is 95504512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21540559 - 2³ = 21540551 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21540559.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1392 + ... + 6709.

It is an arithmetic number, because the mean of its divisors is an integer number (5387830).

Almost surely, 2^21540559 is an apocalyptic number.

21540559 is a deficient number, since it is larger than the sum of its proper divisors (10761).

21540559 is an equidigital number, since it uses as much as digits as its factorization.

21540559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10760.

The product of its (nonzero) digits is 9000, while the sum is 31.

The square root of 21540559 is about 4641.1807764835. The cubic root of 21540559 is about 278.2396317269.

The spelling of 21540559 in words is "twenty-one million, five hundred forty thousand, five hundred fifty-nine".