21090559 has 4 divisors (see below), whose sum is σ = 24103504. Its totient is φ = 18077616.

The previous prime is 21090547. The next prime is 21090583. The reversal of 21090559 is 95509012.

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 21090559 - 2¹⁵ = 21057791 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 21090559.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090529) 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, 1506462 + ... + 1506475.

It is an arithmetic number, because the mean of its divisors is an integer number (6025876).

Almost surely, 2^21090559 is an apocalyptic number.

21090559 is a deficient number, since it is larger than the sum of its proper divisors (3012945).

21090559 is an equidigital number, since it uses as much as digits as its factorization.

21090559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3012944.

The product of its (nonzero) digits is 4050, while the sum is 31.

The square root of 21090559 is about 4592.4458625007. The cubic root of 21090559 is about 276.2884289612.

The spelling of 21090559 in words is "twenty-one million, ninety thousand, five hundred fifty-nine".