20856820 has 24 divisors (see below), whose sum is σ = 43893864. Its totient is φ = 8324736.

The previous prime is 20856793. The next prime is 20856827. The reversal of 20856820 is 2865802.

It can be written as a sum of positive squares in 4 ways, for example, as 8464 + 20848356 = 92^2 + 4566^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20856827) 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 7 ways as a sum of consecutive naturals, for example, 12262 + ... + 13858.

It is an arithmetic number, because the mean of its divisors is an integer number (1828911).

Almost surely, 2^20856820 is an apocalyptic number.

20856820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20856820 is an abundant number, since it is smaller than the sum of its proper divisors (23037044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20856820 is a wasteful number, since it uses less digits than its factorization.

20856820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2259 (or 2257 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 20856820 is about 4566.9267565837. The cubic root of 20856820 is about 275.2639669281.

The spelling of 20856820 in words is "twenty million, eight hundred fifty-six thousand, eight hundred twenty".