20042509 has 4 divisors (see below), whose sum is σ = 20733660. Its totient is φ = 19351360.

The previous prime is 20042489. The next prime is 20042513. The reversal of 20042509 is 90524002.

It is a happy number.

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 14040009 + 6002500 = 3747^2 + 2450^2 .

It is a cyclic number.

It is not a de Polignac number, because 20042509 - 2¹³ = 20034317 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20042509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20042579) 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, 345532 + ... + 345589.

It is an arithmetic number, because the mean of its divisors is an integer number (5183415).

Almost surely, 2^20042509 is an apocalyptic number.

20042509 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

20042509 is a deficient number, since it is larger than the sum of its proper divisors (691151).

20042509 is an equidigital number, since it uses as much as digits as its factorization.

20042509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 691150.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 20042509 is about 4476.8860829822. The cubic root of 20042509 is about 271.6339375344.

The spelling of 20042509 in words is "twenty million, forty-two thousand, five hundred nine".