20421759 has 4 divisors (see below), whose sum is σ = 27229016. Its totient is φ = 13614504.

The previous prime is 20421749. The next prime is 20421767. The reversal of 20421759 is 95712402.

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

It is not a de Polignac number, because 20421759 - 2⁸ = 20421503 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20421719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3403624 + ... + 3403629.

It is an arithmetic number, because the mean of its divisors is an integer number (6807254).

Almost surely, 2^20421759 is an apocalyptic number.

20421759 is a deficient number, since it is larger than the sum of its proper divisors (6807257).

20421759 is an equidigital number, since it uses as much as digits as its factorization.

20421759 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6807256.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 20421759 is about 4519.0440360767. The cubic root of 20421759 is about 273.3365544270.

The spelling of 20421759 in words is "twenty million, four hundred twenty-one thousand, seven hundred fifty-nine".