20155609 has 4 divisors (see below), whose sum is σ = 20850660. Its totient is φ = 19460560.

The previous prime is 20155607. The next prime is 20155627. The reversal of 20155609 is 90655102.

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 3139984 + 17015625 = 1772^2 + 4125^2 .

It is a cyclic number.

It is not a de Polignac number, because 20155609 - 2¹ = 20155607 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20155601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 347482 + ... + 347539.

It is an arithmetic number, because the mean of its divisors is an integer number (5212665).

Almost surely, 2^20155609 is an apocalyptic number.

20155609 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

20155609 is a deficient number, since it is larger than the sum of its proper divisors (695051).

20155609 is an equidigital number, since it uses as much as digits as its factorization.

20155609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 695050.

The product of its (nonzero) digits is 2700, while the sum is 28.

The square root of 20155609 is about 4489.4998607863. The cubic root of 20155609 is about 272.1439234358.

The spelling of 20155609 in words is "twenty million, one hundred fifty-five thousand, six hundred nine".