20493809 has 18 divisors (see below), whose sum is σ = 24665382. Its totient is φ = 16968000.

The previous prime is 20493791. The next prime is 20493839. The reversal of 20493809 is 90839402.

It can be written as a sum of positive squares in 3 ways, for example, as 8439025 + 12054784 = 2905^2 + 3472^2 .

It is not a de Polignac number, because 20493809 - 2⁸ = 20493553 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20493839) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 202859 + ... + 202959.

It is an arithmetic number, because the mean of its divisors is an integer number (1370299).

Almost surely, 2^20493809 is an apocalyptic number.

It is an amenable number.

20493809 is a deficient number, since it is larger than the sum of its proper divisors (4171573).

20493809 is an equidigital number, since it uses as much as digits as its factorization.

20493809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257 (or 149 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 20493809 is about 4527.0088358650. The cubic root of 20493809 is about 273.6576299908.

The spelling of 20493809 in words is "twenty million, four hundred ninety-three thousand, eight hundred nine".