20256509 has 12 divisors (see below), whose sum is σ = 25069536. Its totient is φ = 16026192.

The previous prime is 20256497. The next prime is 20256521. The reversal of 20256509 is 90565202.

It is an interprime number because it is at equal distance from previous prime (20256497) and next prime (20256521).

It is a de Polignac number, because none of the positive numbers 2^k-20256509 is a prime.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20256539) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7379 + ... + 9744.

It is an arithmetic number, because the mean of its divisors is an integer number (2089128).

Almost surely, 2^20256509 is an apocalyptic number.

It is an amenable number.

20256509 is a deficient number, since it is larger than the sum of its proper divisors (4813027).

20256509 is a wasteful number, since it uses less digits than its factorization.

20256509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17156 (or 17143 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 20256509 is about 4500.7231641149. The cubic root of 20256509 is about 272.5972898406.

The spelling of 20256509 in words is "twenty million, two hundred fifty-six thousand, five hundred nine".