20643999 has 8 divisors (see below), whose sum is σ = 28165632. Its totient is φ = 13442520.

The previous prime is 20643947. The next prime is 20644003. The reversal of 20643999 is 99934602.

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

It is not a de Polignac number, because 20643999 - 2⁹ = 20643487 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20643999.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20647999) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79887 + ... + 80144.

It is an arithmetic number, because the mean of its divisors is an integer number (3520704).

Almost surely, 2^20643999 is an apocalyptic number.

20643999 is a deficient number, since it is larger than the sum of its proper divisors (7521633).

20643999 is a wasteful number, since it uses less digits than its factorization.

20643999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160077.

The product of its (nonzero) digits is 104976, while the sum is 42.

The square root of 20643999 is about 4543.5667707210. The cubic root of 20643999 is about 274.3245085179.

The spelling of 20643999 in words is "twenty million, six hundred forty-three thousand, nine hundred ninety-nine".