20681887 has 4 divisors (see below), whose sum is σ = 20839896. Its totient is φ = 20523880.

The previous prime is 20681879. The next prime is 20681891. The reversal of 20681887 is 78818602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78818602 = 2 ⋅39409301.

It is a cyclic number.

It is not a de Polignac number, because 20681887 - 2³ = 20681879 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20651887) 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, 78808 + ... + 79069.

It is an arithmetic number, because the mean of its divisors is an integer number (5209974).

Almost surely, 2^20681887 is an apocalyptic number.

20681887 is a deficient number, since it is larger than the sum of its proper divisors (158009).

20681887 is a wasteful number, since it uses less digits than its factorization.

20681887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158008.

The product of its (nonzero) digits is 43008, while the sum is 40.

The square root of 20681887 is about 4547.7342710409. The cubic root of 20681887 is about 274.4922288480.

The spelling of 20681887 in words is "twenty million, six hundred eighty-one thousand, eight hundred eighty-seven".