21032405 has 4 divisors (see below), whose sum is σ = 25238892. Its totient is φ = 16825920.

The previous prime is 21032399. The next prime is 21032437. The reversal of 21032405 is 50423012.

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 11930116 + 9102289 = 3454^2 + 3017^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21032405 is a prime.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 2103236 + ... + 2103245.

It is an arithmetic number, because the mean of its divisors is an integer number (6309723).

Almost surely, 2^21032405 is an apocalyptic number.

It is an amenable number.

21032405 is a deficient number, since it is larger than the sum of its proper divisors (4206487).

21032405 is an equidigital number, since it uses as much as digits as its factorization.

21032405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4206486.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21032405 is about 4586.1100074028. The cubic root of 21032405 is about 276.0342541327.

Adding to 21032405 its reverse (50423012), we get a palindrome (71455417).

The spelling of 21032405 in words is "twenty-one million, thirty-two thousand, four hundred five".