20806455851 has 4 divisors (see below), whose sum is σ = 20816446632. Its totient is φ = 20796465072.

The previous prime is 20806455827. The next prime is 20806455869. The reversal of 20806455851 is 15855460802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15855460802 = 2 ⋅7927730401.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20806455851 is a prime.

It is a super-2 number, since 2×20806455851² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20806455821) 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, 4992266 + ... + 4996431.

It is an arithmetic number, because the mean of its divisors is an integer number (5204111658).

Almost surely, 2^20806455851 is an apocalyptic number.

20806455851 is a deficient number, since it is larger than the sum of its proper divisors (9990781).

20806455851 is an equidigital number, since it uses as much as digits as its factorization.

20806455851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9990780.

The product of its (nonzero) digits is 384000, while the sum is 44.

The spelling of 20806455851 in words is "twenty billion, eight hundred six million, four hundred fifty-five thousand, eight hundred fifty-one".