20640321 has 12 divisors (see below), whose sum is σ = 32107348. Its totient is φ = 12701664.

The previous prime is 20640317. The next prime is 20640331. The reversal of 20640321 is 12304602.

It is a happy number.

20640321 is a `hidden beast` number, since 2 + 0 + 640 + 3 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 3920400 + 16719921 = 1980^2 + 4089^2 .

It is not a de Polignac number, because 20640321 - 2² = 20640317 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20640294 and 20640303.

It is not an unprimeable number, because it can be changed into a prime (20640331) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 88090 + ... + 88323.

Almost surely, 2^20640321 is an apocalyptic number.

It is an amenable number.

20640321 is a deficient number, since it is larger than the sum of its proper divisors (11467027).

20640321 is a wasteful number, since it uses less digits than its factorization.

20640321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176432 (or 176429 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 20640321 is about 4543.1620045955. The cubic root of 20640321 is about 274.3082160437.

Adding to 20640321 its reverse (12304602), we get a palindrome (32944923).

The spelling of 20640321 in words is "twenty million, six hundred forty thousand, three hundred twenty-one".