20421305 has 4 divisors (see below), whose sum is σ = 24505572. Its totient is φ = 16337040.

The previous prime is 20421287. The next prime is 20421329. The reversal of 20421305 is 50312402.

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 9504889 + 10916416 = 3083^2 + 3304^2 .

It is not a de Polignac number, because 20421305 - 2⁶ = 20421241 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2042126 + ... + 2042135.

It is an arithmetic number, because the mean of its divisors is an integer number (6126393).

Almost surely, 2^20421305 is an apocalyptic number.

It is an amenable number.

20421305 is a deficient number, since it is larger than the sum of its proper divisors (4084267).

20421305 is an equidigital number, since it uses as much as digits as its factorization.

20421305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4084266.

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

The square root of 20421305 is about 4518.9938039347. The cubic root of 20421305 is about 273.3345288797.

Adding to 20421305 its reverse (50312402), we get a palindrome (70733707).

The spelling of 20421305 in words is "twenty million, four hundred twenty-one thousand, three hundred five".