20945909 has 4 divisors (see below), whose sum is σ = 21021804. Its totient is φ = 20870016.

The previous prime is 20945891. The next prime is 20945927. The reversal of 20945909 is 90954902.

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

It is an interprime number because it is at equal distance from previous prime (20945891) and next prime (20945927).

It can be written as a sum of positive squares in 2 ways, for example, as 4502884 + 16443025 = 2122^2 + 4055^2 .

It is a cyclic number.

It is not a de Polignac number, because 20945909 - 2²⁰ = 19897333 is a prime.

It is a super-2 number, since 2×20945909² = 877462207672562, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20945209) 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, 37532 + ... + 38085.

It is an arithmetic number, because the mean of its divisors is an integer number (5255451).

Almost surely, 2^20945909 is an apocalyptic number.

It is an amenable number.

20945909 is a deficient number, since it is larger than the sum of its proper divisors (75895).

20945909 is an equidigital number, since it uses as much as digits as its factorization.

20945909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75894.

The product of its (nonzero) digits is 29160, while the sum is 38.

The square root of 20945909 is about 4576.6700776875. The cubic root of 20945909 is about 275.6553362400.

The spelling of 20945909 in words is "twenty million, nine hundred forty-five thousand, nine hundred nine".