20640638 has 8 divisors (see below), whose sum is σ = 31545288. Its totient is φ = 10125544.

The previous prime is 20640617. The next prime is 20640647. The reversal of 20640638 is 83604602.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20640638.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97256 + ... + 97467.

It is an arithmetic number, because the mean of its divisors is an integer number (3943161).

Almost surely, 2^20640638 is an apocalyptic number.

20640638 is a deficient number, since it is larger than the sum of its proper divisors (10904650).

20640638 is a wasteful number, since it uses less digits than its factorization.

20640638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 194778.

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 20640638 is about 4543.1968920574. The cubic root of 20640638 is about 274.3096203380.

The spelling of 20640638 in words is "twenty million, six hundred forty thousand, six hundred thirty-eight".