20643940 has 24 divisors (see below), whose sum is σ = 44848440. Its totient is φ = 7972608.

The previous prime is 20643907. The next prime is 20643941. The reversal of 20643940 is 4934602.

It can be written as a sum of positive squares in 4 ways, for example, as 68644 + 20575296 = 262^2 + 4536^2 .

It is a junction number, because it is equal to n+sod(n) for n = 20643899 and 20643908.

It is not an unprimeable number, because it can be changed into a prime (20643941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17217 + ... + 18376.

It is an arithmetic number, because the mean of its divisors is an integer number (1868685).

Almost surely, 2^20643940 is an apocalyptic number.

20643940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20643940 is an abundant number, since it is smaller than the sum of its proper divisors (24204500).

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

20643940 is a wasteful number, since it uses less digits than its factorization.

20643940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35631 (or 35629 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 20643940 is about 4543.5602780199. The cubic root of 20643940 is about 274.3242471803.

The spelling of 20643940 in words is "twenty million, six hundred forty-three thousand, nine hundred forty".