20424209 has 4 divisors (see below), whose sum is σ = 21995316. Its totient is φ = 18853104.

The previous prime is 20424199. The next prime is 20424247. The reversal of 20424209 is 90242402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90242402 = 2 ⋅45121201.

It can be written as a sum of positive squares in 2 ways, for example, as 8673025 + 11751184 = 2945^2 + 3428^2 .

It is a cyclic number.

It is not a de Polignac number, because 20424209 - 2⁴ = 20424193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20424409) 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, 785534 + ... + 785559.

It is an arithmetic number, because the mean of its divisors is an integer number (5498829).

Almost surely, 2^20424209 is an apocalyptic number.

It is an amenable number.

20424209 is a deficient number, since it is larger than the sum of its proper divisors (1571107).

20424209 is a wasteful number, since it uses less digits than its factorization.

20424209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1571106.

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 20424209 is about 4519.3151029774. The cubic root of 20424209 is about 273.3474847257.

The spelling of 20424209 in words is "twenty million, four hundred twenty-four thousand, two hundred nine".