21532505 has 4 divisors (see below), whose sum is σ = 25839012. Its totient is φ = 17226000.

The previous prime is 21532501. The next prime is 21532513. The reversal of 21532505 is 50523512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11916304 + 9616201 = 3452^2 + 3101^2 .

It is not a de Polignac number, because 21532505 - 2² = 21532501 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21532501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2153246 + ... + 2153255.

It is an arithmetic number, because the mean of its divisors is an integer number (6459753).

Almost surely, 2^21532505 is an apocalyptic number.

It is an amenable number.

21532505 is a deficient number, since it is larger than the sum of its proper divisors (4306507).

21532505 is an equidigital number, since it uses as much as digits as its factorization.

21532505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4306506.

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 21532505 is about 4640.3130282342. The cubic root of 21532505 is about 278.2049495359.

The spelling of 21532505 in words is "twenty-one million, five hundred thirty-two thousand, five hundred five".