21605829 has 16 divisors (see below), whose sum is σ = 33062400. Its totient is φ = 12294000.

The previous prime is 21605807. The next prime is 21605833. The reversal of 21605829 is 92850612.

It is not a de Polignac number, because 21605829 - 2¹³ = 21597637 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21605829.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605849) 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 15 ways as a sum of consecutive naturals, for example, 3222 + ... + 7320.

It is an arithmetic number, because the mean of its divisors is an integer number (2066400).

Almost surely, 2^21605829 is an apocalyptic number.

It is an amenable number.

21605829 is a deficient number, since it is larger than the sum of its proper divisors (11456571).

21605829 is a wasteful number, since it uses less digits than its factorization.

21605829 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4360.

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 21605829 is about 4648.2070737006. The cubic root of 21605829 is about 278.5203794500.

The spelling of 21605829 in words is "twenty-one million, six hundred five thousand, eight hundred twenty-nine".