20806681 has 4 divisors (see below), whose sum is σ = 23779072. Its totient is φ = 17834292.

The previous prime is 20806663. The next prime is 20806693. The reversal of 20806681 is 18660802.

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 not a de Polignac number, because 20806681 - 2⁷ = 20806553 is a prime.

It is a super-2 number, since 2×20806681² = 865835948471522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20806631) 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, 1486185 + ... + 1486198.

It is an arithmetic number, because the mean of its divisors is an integer number (5944768).

Almost surely, 2^20806681 is an apocalyptic number.

It is an amenable number.

20806681 is a deficient number, since it is larger than the sum of its proper divisors (2972391).

20806681 is an equidigital number, since it uses as much as digits as its factorization.

20806681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2972390.

The product of its (nonzero) digits is 4608, while the sum is 31.

The square root of 20806681 is about 4561.4340946680. The cubic root of 20806681 is about 275.0432152471.

The spelling of 20806681 in words is "twenty million, eight hundred six thousand, six hundred eighty-one".