20541509 has 4 divisors (see below), whose sum is σ = 20655180. Its totient is φ = 20427840.

The previous prime is 20541497. The next prime is 20541511. The reversal of 20541509 is 90514502.

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 605284 + 19936225 = 778^2 + 4465^2 .

It is a cyclic number.

It is not a de Polignac number, because 20541509 - 2²⁰ = 19492933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20549509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 56564 + ... + 56925.

It is an arithmetic number, because the mean of its divisors is an integer number (5163795).

Almost surely, 2^20541509 is an apocalyptic number.

It is an amenable number.

20541509 is a deficient number, since it is larger than the sum of its proper divisors (113671).

20541509 is a wasteful number, since it uses less digits than its factorization.

20541509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113670.

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 20541509 is about 4532.2741532259. The cubic root of 20541509 is about 273.8697811266.

It can be divided in two parts, 205 and 41509, that added together give a palindrome (41714).

The spelling of 20541509 in words is "twenty million, five hundred forty-one thousand, five hundred nine".