20556851 has 4 divisors (see below), whose sum is σ = 23493552. Its totient is φ = 17620152.

The previous prime is 20556829. The next prime is 20556857. The reversal of 20556851 is 15865502.

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

It is a cyclic number.

It is not a de Polignac number, because 20556851 - 2⁶ = 20556787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20556857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1468340 + ... + 1468353.

It is an arithmetic number, because the mean of its divisors is an integer number (5873388).

Almost surely, 2^20556851 is an apocalyptic number.

20556851 is a deficient number, since it is larger than the sum of its proper divisors (2936701).

20556851 is an equidigital number, since it uses as much as digits as its factorization.

20556851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2936700.

The product of its (nonzero) digits is 12000, while the sum is 32.

The square root of 20556851 is about 4533.9663651156. The cubic root of 20556851 is about 273.9379465920.

The spelling of 20556851 in words is "twenty million, five hundred fifty-six thousand, eight hundred fifty-one".