20509109 has 2 divisors, whose sum is σ = 20509110. Its totient is φ = 20509108.

The previous prime is 20509081. The next prime is 20509117. The reversal of 20509109 is 90190502.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18464209 + 2044900 = 4297^2 + 1430^2 .

It is a cyclic number.

It is not a de Polignac number, because 20509109 - 2⁸ = 20508853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20509129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10254554 + 10254555.

It is an arithmetic number, because the mean of its divisors is an integer number (10254555).

Almost surely, 2^20509109 is an apocalyptic number.

It is an amenable number.

20509109 is a deficient number, since it is larger than the sum of its proper divisors (1).

20509109 is an equidigital number, since it uses as much as digits as its factorization.

20509109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 810, while the sum is 26.

The square root of 20509109 is about 4528.6983781215. The cubic root of 20509109 is about 273.7257142957.

The spelling of 20509109 in words is "twenty million, five hundred nine thousand, one hundred nine".