20819555 has 4 divisors (see below), whose sum is σ = 24983472. Its totient is φ = 16655640.

The previous prime is 20819521. The next prime is 20819563. The reversal of 20819555 is 55591802.

It is a semiprime because it is the product of two primes.

It is a de Polignac number, because none of the positive numbers 2^k-20819555 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2081951 + ... + 2081960.

It is an arithmetic number, because the mean of its divisors is an integer number (6245868).

Almost surely, 2^20819555 is an apocalyptic number.

20819555 is a deficient number, since it is larger than the sum of its proper divisors (4163917).

20819555 is an equidigital number, since it uses as much as digits as its factorization.

20819555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4163916.

The product of its (nonzero) digits is 18000, while the sum is 35.

The square root of 20819555 is about 4562.8450554451. The cubic root of 20819555 is about 275.0999306246.

The spelling of 20819555 in words is "twenty million, eight hundred nineteen thousand, five hundred fifty-five".