20731680 has 96 divisors (see below), whose sum is σ = 72576000. Its totient is φ = 5527296.

The previous prime is 20731663. The next prime is 20731681. The reversal of 20731680 is 8613702.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20731681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1921 + ... + 6719.

It is an arithmetic number, because the mean of its divisors is an integer number (756000).

Almost surely, 2^20731680 is an apocalyptic number.

20731680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

20731680 is the 2880-th heptagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20731680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36288000).

20731680 is an abundant number, since it is smaller than the sum of its proper divisors (51844320).

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

20731680 is a wasteful number, since it uses less digits than its factorization.

20731680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4823 (or 4809 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 20731680 is about 4553.2054642856. The cubic root of 20731680 is about 274.7123383170.

The spelling of 20731680 in words is "twenty million, seven hundred thirty-one thousand, six hundred eighty".