20439989 has 4 divisors (see below), whose sum is σ = 20589324. Its totient is φ = 20290656.

The previous prime is 20439959. The next prime is 20440039. The reversal of 20439989 is 98993402.

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 4774225 + 15665764 = 2185^2 + 3958^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20439989 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 (20439919) 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, 74462 + ... + 74735.

It is an arithmetic number, because the mean of its divisors is an integer number (5147331).

Almost surely, 2^20439989 is an apocalyptic number.

It is an amenable number.

20439989 is a deficient number, since it is larger than the sum of its proper divisors (149335).

20439989 is a wasteful number, since it uses less digits than its factorization.

20439989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149334.

The product of its (nonzero) digits is 139968, while the sum is 44.

The square root of 20439989 is about 4521.0606056544. The cubic root of 20439989 is about 273.4178638351.

The spelling of 20439989 in words is "twenty million, four hundred thirty-nine thousand, nine hundred eighty-nine".