20851320 has 128 divisors (see below), whose sum is σ = 72483840. Its totient is φ = 4700160.

The previous prime is 20851301. The next prime is 20851321. The reversal of 20851320 is 2315802.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20851321) 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 31 ways as a sum of consecutive naturals, for example, 86400 + ... + 86640.

It is an arithmetic number, because the mean of its divisors is an integer number (566280).

Almost surely, 2^20851320 is an apocalyptic number.

20851320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20851320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36241920).

20851320 is an abundant number, since it is smaller than the sum of its proper divisors (51632520).

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

20851320 is a wasteful number, since it uses less digits than its factorization.

20851320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365 (or 361 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 20851320 is about 4566.3245613951. The cubic root of 20851320 is about 275.2397688494.

The spelling of 20851320 in words is "twenty million, eight hundred fifty-one thousand, three hundred twenty".