21528005 has 8 divisors (see below), whose sum is σ = 26724600. Its totient is φ = 16628416.

The previous prime is 21527983. The next prime is 21528011. The reversal of 21528005 is 50082512.

It can be written as a sum of positive squares in 4 ways, for example, as 1079521 + 20448484 = 1039^2 + 4522^2 .

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 21528005 - 2⁸ = 21527749 is a prime.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 74090 + ... + 74379.

It is an arithmetic number, because the mean of its divisors is an integer number (3340575).

Almost surely, 2^21528005 is an apocalyptic number.

It is an amenable number.

21528005 is a deficient number, since it is larger than the sum of its proper divisors (5196595).

21528005 is a wasteful number, since it uses less digits than its factorization.

21528005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148503.

The product of its (nonzero) digits is 800, while the sum is 23.

The square root of 21528005 is about 4639.8281218166. The cubic root of 21528005 is about 278.1855678384.

The spelling of 21528005 in words is "twenty-one million, five hundred twenty-eight thousand, five".