20643541 has 4 divisors (see below), whose sum is σ = 21147084. Its totient is φ = 20140000.

The previous prime is 20643529. The next prime is 20643547. The reversal of 20643541 is 14534602.

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 9394225 + 11249316 = 3065^2 + 3354^2 .

It is a cyclic number.

It is not a de Polignac number, because 20643541 - 2⁵ = 20643509 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 (20643547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 251710 + ... + 251791.

It is an arithmetic number, because the mean of its divisors is an integer number (5286771).

Almost surely, 2^20643541 is an apocalyptic number.

It is an amenable number.

20643541 is a deficient number, since it is larger than the sum of its proper divisors (503543).

20643541 is an equidigital number, since it uses as much as digits as its factorization.

20643541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 503542.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 20643541 is about 4543.5163695094. The cubic root of 20643541 is about 274.3224798161.

The spelling of 20643541 in words is "twenty million, six hundred forty-three thousand, five hundred forty-one".