21605330 has 8 divisors (see below), whose sum is σ = 38889612. Its totient is φ = 8642128.

The previous prime is 21605329. The next prime is 21605369. The reversal of 21605330 is 3350612.

It can be written as a sum of positive squares in 2 ways, for example, as 20529961 + 1075369 = 4531^2 + 1037^2 .

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

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 1080257 + ... + 1080276.

Almost surely, 2^21605330 is an apocalyptic number.

21605330 is a deficient number, since it is larger than the sum of its proper divisors (17284282).

21605330 is a wasteful number, since it uses less digits than its factorization.

21605330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2160540.

The product of its (nonzero) digits is 540, while the sum is 20.

The square root of 21605330 is about 4648.1533967803. The cubic root of 21605330 is about 278.5182352333.

Adding to 21605330 its reverse (3350612), we get a palindrome (24955942).

The spelling of 21605330 in words is "twenty-one million, six hundred five thousand, three hundred thirty".