20644385 has 4 divisors (see below), whose sum is σ = 24773268. Its totient is φ = 16515504.

The previous prime is 20644369. The next prime is 20644387. The reversal of 20644385 is 58344602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 58344602 = 2 ⋅29172301.

It can be written as a sum of positive squares in 2 ways, for example, as 11888704 + 8755681 = 3448^2 + 2959^2 .

It is a cyclic number.

It is not a de Polignac number, because 20644385 - 2⁴ = 20644369 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20644387) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2064434 + ... + 2064443.

It is an arithmetic number, because the mean of its divisors is an integer number (6193317).

Almost surely, 2^20644385 is an apocalyptic number.

It is an amenable number.

20644385 is a deficient number, since it is larger than the sum of its proper divisors (4128883).

20644385 is an equidigital number, since it uses as much as digits as its factorization.

20644385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4128882.

The product of its (nonzero) digits is 23040, while the sum is 32.

The square root of 20644385 is about 4543.6092481638. The cubic root of 20644385 is about 274.3262182739.

Adding to 20644385 its reverse (58344602), we get a palindrome (78988987).

The spelling of 20644385 in words is "twenty million, six hundred forty-four thousand, three hundred eighty-five".