21612559 has 8 divisors (see below), whose sum is σ = 22967280. Its totient is φ = 20267136.

The previous prime is 21612529. The next prime is 21612581. The reversal of 21612559 is 95521612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21612559 - 2⁷ = 21612431 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 21612559.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21612509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2812 + ... + 7150.

It is an arithmetic number, because the mean of its divisors is an integer number (2870910).

Almost surely, 2^21612559 is an apocalyptic number.

21612559 is a deficient number, since it is larger than the sum of its proper divisors (1354721).

21612559 is a wasteful number, since it uses less digits than its factorization.

21612559 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4649.

The product of its digits is 5400, while the sum is 31.

The square root of 21612559 is about 4648.9309523803. The cubic root of 21612559 is about 278.5492952203.

The spelling of 21612559 in words is "twenty-one million, six hundred twelve thousand, five hundred fifty-nine".