20640868 has 6 divisors (see below), whose sum is σ = 36121526. Its totient is φ = 10320432.

The previous prime is 20640847. The next prime is 20640869. The reversal of 20640868 is 86804602.

It can be written as a sum of positive squares in only one way, i.e., 17791524 + 2849344 = 4218^2 + 1688^2 .

It is not an unprimeable number, because it can be changed into a prime (20640869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2580105 + ... + 2580112.

Almost surely, 2^20640868 is an apocalyptic number.

It is an amenable number.

20640868 is a deficient number, since it is larger than the sum of its proper divisors (15480658).

20640868 is a wasteful number, since it uses less digits than its factorization.

20640868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5160221 (or 5160219 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 34.

The square root of 20640868 is about 4543.2222045592. Note that the first 4 decimals coincide. The cubic root of 20640868 is about 274.3106392177.

The spelling of 20640868 in words is "twenty million, six hundred forty thousand, eight hundred sixty-eight".