20656871 has 4 divisors (see below), whose sum is σ = 20675544. Its totient is φ = 20638200.

The previous prime is 20656849. The next prime is 20656873. The reversal of 20656871 is 17865602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17865602 = 2 ⋅8932801.

It is a cyclic number.

It is not a de Polignac number, because 20656871 - 2¹⁸ = 20394727 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 (20656873) 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, 7565 + ... + 9926.

It is an arithmetic number, because the mean of its divisors is an integer number (5168886).

Almost surely, 2^20656871 is an apocalyptic number.

20656871 is a deficient number, since it is larger than the sum of its proper divisors (18673).

20656871 is a wasteful number, since it uses less digits than its factorization.

20656871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18672.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 20656871 is about 4544.9830582743. The cubic root of 20656871 is about 274.3815125157.

The spelling of 20656871 in words is "twenty million, six hundred fifty-six thousand, eight hundred seventy-one".