21728611 has 8 divisors (see below), whose sum is σ = 22024800. Its totient is φ = 21434688.

The previous prime is 21728593. The next prime is 21728621. The reversal of 21728611 is 11682712.

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

It is not a de Polignac number, because 21728611 - 2¹⁷ = 21597539 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 21728611.

It is not an unprimeable number, because it can be changed into a prime (21728621) 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 7 ways as a sum of consecutive naturals, for example, 26865 + ... + 27661.

It is an arithmetic number, because the mean of its divisors is an integer number (2753100).

Almost surely, 2^21728611 is an apocalyptic number.

21728611 is a deficient number, since it is larger than the sum of its proper divisors (296189).

21728611 is a wasteful number, since it uses less digits than its factorization.

21728611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133.

The product of its digits is 1344, while the sum is 28.

The square root of 21728611 is about 4661.3958209961. The cubic root of 21728611 is about 279.0469767551.

The spelling of 21728611 in words is "twenty-one million, seven hundred twenty-eight thousand, six hundred eleven".