20638913 has 4 divisors (see below), whose sum is σ = 20789700. Its totient is φ = 20488128.

The previous prime is 20638861. The next prime is 20638931. The reversal of 20638913 is 31983602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12159169 + 8479744 = 3487^2 + 2912^2 .

It is a cyclic number.

It is not a de Polignac number, because 20638913 - 2¹⁴ = 20622529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20638913.

It is not an unprimeable number, because it can be changed into a prime (20638973) 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 in 3 ways as a sum of consecutive naturals, for example, 75188 + ... + 75461.

It is an arithmetic number, because the mean of its divisors is an integer number (5197425).

Almost surely, 2^20638913 is an apocalyptic number.

It is an amenable number.

20638913 is a deficient number, since it is larger than the sum of its proper divisors (150787).

20638913 is a wasteful number, since it uses less digits than its factorization.

20638913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150786.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 20638913 is about 4543.0070437982. The cubic root of 20638913 is about 274.3019784993.

The spelling of 20638913 in words is "twenty million, six hundred thirty-eight thousand, nine hundred thirteen".