21328505 has 8 divisors (see below), whose sum is σ = 27921024. Its totient is φ = 15511600.

The previous prime is 21328501. The next prime is 21328537. The reversal of 21328505 is 50582312.

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

It is not a de Polignac number, because 21328505 - 2² = 21328501 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21328501) 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, 193841 + ... + 193950.

It is an arithmetic number, because the mean of its divisors is an integer number (3490128).

Almost surely, 2^21328505 is an apocalyptic number.

It is an amenable number.

21328505 is a deficient number, since it is larger than the sum of its proper divisors (6592519).

21328505 is a wasteful number, since it uses less digits than its factorization.

21328505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 387807.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 21328505 is about 4618.2794415237. The cubic root of 21328505 is about 277.3235845406.

The spelling of 21328505 in words is "twenty-one million, three hundred twenty-eight thousand, five hundred five".