20428809 has 16 divisors (see below), whose sum is σ = 27882240. Its totient is φ = 13300560.

The previous prime is 20428801. The next prime is 20428817. The reversal of 20428809 is 90882402.

It is an interprime number because it is at equal distance from previous prime (20428801) and next prime (20428817).

It is not a de Polignac number, because 20428809 - 2³ = 20428801 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20428809.

It is not an unprimeable number, because it can be changed into a prime (20428801) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37074 + ... + 37620.

It is an arithmetic number, because the mean of its divisors is an integer number (1742640).

Almost surely, 2^20428809 is an apocalyptic number.

It is an amenable number.

20428809 is a deficient number, since it is larger than the sum of its proper divisors (7453431).

20428809 is a wasteful number, since it uses less digits than its factorization.

20428809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 820.

The product of its (nonzero) digits is 9216, while the sum is 33.

The square root of 20428809 is about 4519.8240009983. The cubic root of 20428809 is about 273.3680045582.

The spelling of 20428809 in words is "twenty million, four hundred twenty-eight thousand, eight hundred nine".