20509091 has 4 divisors (see below), whose sum is σ = 20571384. Its totient is φ = 20446800.

The previous prime is 20509081. The next prime is 20509109. The reversal of 20509091 is 19090502.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20509091 - 2¹⁴ = 20492707 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 20509091.

It is not an unprimeable number, because it can be changed into a prime (20509081) 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, 30650 + ... + 31311.

It is an arithmetic number, because the mean of its divisors is an integer number (5142846).

Almost surely, 2^20509091 is an apocalyptic number.

20509091 is a deficient number, since it is larger than the sum of its proper divisors (62293).

20509091 is an equidigital number, since it uses as much as digits as its factorization.

20509091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62292.

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

The square root of 20509091 is about 4528.6963907950. The cubic root of 20509091 is about 273.7256342164.

Adding to 20509091 its reverse (19090502), we get a palindrome (39599593).

The spelling of 20509091 in words is "twenty million, five hundred nine thousand, ninety-one".