21659559 has 16 divisors (see below), whose sum is σ = 29513088. Its totient is φ = 14126112.

The previous prime is 21659557. The next prime is 21659569. The reversal of 21659559 is 95595612.

It is not a de Polignac number, because 21659559 - 2¹ = 21659557 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21659559.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21659557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39324 + ... + 39870.

It is an arithmetic number, because the mean of its divisors is an integer number (1844568).

Almost surely, 2^21659559 is an apocalyptic number.

21659559 is a deficient number, since it is larger than the sum of its proper divisors (7853529).

21659559 is a wasteful number, since it uses less digits than its factorization.

21659559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 814.

The product of its digits is 121500, while the sum is 42.

The square root of 21659559 is about 4653.9831327584. The cubic root of 21659559 is about 278.7510658395.

It can be divided in two parts, 2 and 1659559, that added together give a palindrome (1659561).

The spelling of 21659559 in words is "twenty-one million, six hundred fifty-nine thousand, five hundred fifty-nine".