20840047 has 4 divisors (see below), whose sum is σ = 21746160. Its totient is φ = 19933936.

The previous prime is 20840041. The next prime is 20840059. The reversal of 20840047 is 74004802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74004802 = 2 ⋅37002401.

It is a cyclic number.

It is not a de Polignac number, because 20840047 - 2⁷ = 20839919 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 (20840041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 453022 + ... + 453067.

It is an arithmetic number, because the mean of its divisors is an integer number (5436540).

Almost surely, 2^20840047 is an apocalyptic number.

20840047 is a deficient number, since it is larger than the sum of its proper divisors (906113).

20840047 is an equidigital number, since it uses as much as digits as its factorization.

20840047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 906112.

The product of its (nonzero) digits is 1792, while the sum is 25.

The square root of 20840047 is about 4565.0900319709. The cubic root of 20840047 is about 275.1901582853.

Adding to 20840047 its reverse (74004802), we get a palindrome (94844849).

The spelling of 20840047 in words is "twenty million, eight hundred forty thousand, forty-seven".