20643959 has 4 divisors (see below), whose sum is σ = 23593104. Its totient is φ = 17694816.

The previous prime is 20643947. The next prime is 20644003. The reversal of 20643959 is 95934602.

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

It is a cyclic number.

It is not a de Polignac number, because 20643959 - 2⁴ = 20643943 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20633959) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1474562 + ... + 1474575.

It is an arithmetic number, because the mean of its divisors is an integer number (5898276).

Almost surely, 2^20643959 is an apocalyptic number.

20643959 is a deficient number, since it is larger than the sum of its proper divisors (2949145).

20643959 is an equidigital number, since it uses as much as digits as its factorization.

20643959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2949144.

The product of its (nonzero) digits is 58320, while the sum is 38.

The square root of 20643959 is about 4543.5623688907. The cubic root of 20643959 is about 274.3243313399.

The spelling of 20643959 in words is "twenty million, six hundred forty-three thousand, nine hundred fifty-nine".