20644040 has 32 divisors (see below), whose sum is σ = 47148480. Its totient is φ = 8133312.

The previous prime is 20644037. The next prime is 20644049. The reversal of 20644040 is 4044602.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (20644049) 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, 1172 + ... + 6531.

It is an arithmetic number, because the mean of its divisors is an integer number (1473390).

Almost surely, 2^20644040 is an apocalyptic number.

20644040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20644040 is an abundant number, since it is smaller than the sum of its proper divisors (26504440).

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

20644040 is a wasteful number, since it uses less digits than its factorization.

20644040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7781 (or 7777 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 20644040 is about 4543.5712825926. The cubic root of 20644040 is about 274.3246901251.

Adding to 20644040 its reverse (4044602), we get a palindrome (24688642).

The spelling of 20644040 in words is "twenty million, six hundred forty-four thousand, forty".