20805493 has 4 divisors (see below), whose sum is σ = 20823040. Its totient is φ = 20787948.

The previous prime is 20805487. The next prime is 20805497. The reversal of 20805493 is 39450802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20805493 - 2⁵ = 20805461 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 (20805497) 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, 6855 + ... + 9412.

It is an arithmetic number, because the mean of its divisors is an integer number (5205760).

Almost surely, 2^20805493 is an apocalyptic number.

It is an amenable number.

20805493 is a deficient number, since it is larger than the sum of its proper divisors (17547).

20805493 is a wasteful number, since it uses less digits than its factorization.

20805493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17546.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 20805493 is about 4561.3038706054. The cubic root of 20805493 is about 275.0379804292.

The spelling of 20805493 in words is "twenty million, eight hundred five thousand, four hundred ninety-three".