20509305 has 16 divisors (see below), whose sum is σ = 32904960. Its totient is φ = 10908288.

The previous prime is 20509301. The next prime is 20509309. The reversal of 20509305 is 50390502.

It is an interprime number because it is at equal distance from previous prime (20509301) and next prime (20509309).

It is not a de Polignac number, because 20509305 - 2² = 20509301 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20509301) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4464 + ... + 7806.

It is an arithmetic number, because the mean of its divisors is an integer number (2056560).

Almost surely, 2^20509305 is an apocalyptic number.

It is an amenable number.

20509305 is a deficient number, since it is larger than the sum of its proper divisors (12395655).

20509305 is a wasteful number, since it uses less digits than its factorization.

20509305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3760.

The product of its (nonzero) digits is 1350, while the sum is 24.

The square root of 20509305 is about 4528.7200178417. The cubic root of 20509305 is about 273.7265862671.

Adding to 20509305 its reverse (50390502), we get a palindrome (70899807).

The spelling of 20509305 in words is "twenty million, five hundred nine thousand, three hundred five".