20081009 has 4 divisors (see below), whose sum is σ = 21625716. Its totient is φ = 18536304.

The previous prime is 20081003. The next prime is 20081023. The reversal of 20081009 is 90018002.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90018002 = 2 ⋅45009001.

It can be written as a sum of positive squares in 2 ways, for example, as 2650384 + 17430625 = 1628^2 + 4175^2 .

It is a cyclic number.

It is not a de Polignac number, because 20081009 - 2⁴ = 20080993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20081003) 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, 772334 + ... + 772359.

It is an arithmetic number, because the mean of its divisors is an integer number (5406429).

Almost surely, 2^20081009 is an apocalyptic number.

It is an amenable number.

20081009 is a deficient number, since it is larger than the sum of its proper divisors (1544707).

20081009 is a wasteful number, since it uses less digits than its factorization.

20081009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1544706.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 20081009 is about 4481.1838837521. The cubic root of 20081009 is about 271.8077550519.

The spelling of 20081009 in words is "twenty million, eighty-one thousand, nine".