20640343 has 4 divisors (see below), whose sum is σ = 21143808. Its totient is φ = 20136880.

The previous prime is 20640331. The next prime is 20640391. The reversal of 20640343 is 34304602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34304602 = 2 ⋅17152301.

It is a cyclic number.

It is not a de Polignac number, because 20640343 - 2¹⁷ = 20509271 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640313) 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, 251671 + ... + 251752.

It is an arithmetic number, because the mean of its divisors is an integer number (5285952).

Almost surely, 2^20640343 is an apocalyptic number.

20640343 is a deficient number, since it is larger than the sum of its proper divisors (503465).

20640343 is an equidigital number, since it uses as much as digits as its factorization.

20640343 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 503464.

The product of its (nonzero) digits is 1728, while the sum is 22.

The square root of 20640343 is about 4543.1644258160. The cubic root of 20640343 is about 274.3083135030.

Adding to 20640343 its reverse (34304602), we get a palindrome (54944945).

The spelling of 20640343 in words is "twenty million, six hundred forty thousand, three hundred forty-three".