20865919 has 4 divisors (see below), whose sum is σ = 22093344. Its totient is φ = 19638496.

The previous prime is 20865863. The next prime is 20865931. The reversal of 20865919 is 91956802.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20865919 is a prime.

It is a super-2 number, since 2×20865919² = 870773151429122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20865319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 613687 + ... + 613720.

It is an arithmetic number, because the mean of its divisors is an integer number (5523336).

Almost surely, 2^20865919 is an apocalyptic number.

20865919 is a deficient number, since it is larger than the sum of its proper divisors (1227425).

20865919 is a wasteful number, since it uses less digits than its factorization.

20865919 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1227424.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 20865919 is about 4567.9228320978. The cubic root of 20865919 is about 275.3039900109.

The spelling of 20865919 in words is "twenty million, eight hundred sixty-five thousand, nine hundred nineteen".