20856009 has 8 divisors (see below), whose sum is σ = 29017152. Its totient is φ = 13299440.

The previous prime is 20856007. The next prime is 20856023. The reversal of 20856009 is 90065802.

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

It is a cyclic number.

It is not a de Polignac number, because 20856009 - 2¹ = 20856007 is a prime.

It is a super-2 number, since 2×20856009² = 869946222816162, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20856001) 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, 151062 + ... + 151199.

It is an arithmetic number, because the mean of its divisors is an integer number (3627144).

Almost surely, 2^20856009 is an apocalyptic number.

It is an amenable number.

20856009 is a deficient number, since it is larger than the sum of its proper divisors (8161143).

20856009 is a wasteful number, since it uses less digits than its factorization.

20856009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 302287.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 20856009 is about 4566.8379651571. The cubic root of 20856009 is about 275.2603990788.

The spelling of 20856009 in words is "twenty million, eight hundred fifty-six thousand, nine".