20656509 has 8 divisors (see below), whose sum is σ = 28430592. Its totient is φ = 13326720.

The previous prime is 20656499. The next prime is 20656511. The reversal of 20656509 is 90565602.

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

It is not a de Polignac number, because 20656509 - 2⁸ = 20656253 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20656509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20656529) 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, 110964 + ... + 111149.

It is an arithmetic number, because the mean of its divisors is an integer number (3553824).

Almost surely, 2^20656509 is an apocalyptic number.

It is an amenable number.

20656509 is a deficient number, since it is larger than the sum of its proper divisors (7774083).

20656509 is a wasteful number, since it uses less digits than its factorization.

20656509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222147.

The product of its (nonzero) digits is 16200, while the sum is 33.

The square root of 20656509 is about 4544.9432339689. The cubic root of 20656509 is about 274.3799097127.

Adding to 20656509 its reverse (90565602), we get a palindrome (111222111).

The spelling of 20656509 in words is "twenty million, six hundred fifty-six thousand, five hundred nine".