21352505 has 4 divisors (see below), whose sum is σ = 25623012. Its totient is φ = 17082000.

The previous prime is 21352483. The next prime is 21352517. The reversal of 21352505 is 50525312.

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 3400336 + 17952169 = 1844^2 + 4237^2 .

It is not a de Polignac number, because 21352505 - 2⁸ = 21352249 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2135246 + ... + 2135255.

It is an arithmetic number, because the mean of its divisors is an integer number (6405753).

Almost surely, 2^21352505 is an apocalyptic number.

It is an amenable number.

21352505 is a deficient number, since it is larger than the sum of its proper divisors (4270507).

21352505 is an equidigital number, since it uses as much as digits as its factorization.

21352505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4270506.

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

The square root of 21352505 is about 4620.8770812477. The cubic root of 21352505 is about 277.4275654355.

Adding to 21352505 its reverse (50525312), we get a palindrome (71877817).

The spelling of 21352505 in words is "twenty-one million, three hundred fifty-two thousand, five hundred five".