20391287 has 4 divisors (see below), whose sum is σ = 23304336. Its totient is φ = 17478240.

The previous prime is 20391281. The next prime is 20391289. The reversal of 20391287 is 78219302.

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

It is a cyclic number.

It is not a de Polignac number, because 20391287 - 2¹⁰ = 20390263 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 (20391281) 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, 1456514 + ... + 1456527.

It is an arithmetic number, because the mean of its divisors is an integer number (5826084).

Almost surely, 2^20391287 is an apocalyptic number.

20391287 is a deficient number, since it is larger than the sum of its proper divisors (2913049).

20391287 is an equidigital number, since it uses as much as digits as its factorization.

20391287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2913048.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 20391287 is about 4515.6712679291. The cubic root of 20391287 is about 273.2005351670.

The spelling of 20391287 in words is "twenty million, three hundred ninety-one thousand, two hundred eighty-seven".