20731287 has 4 divisors (see below), whose sum is σ = 27641720. Its totient is φ = 13820856.

The previous prime is 20731283. The next prime is 20731301. The reversal of 20731287 is 78213702.

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

It is not a de Polignac number, because 20731287 - 2² = 20731283 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 (20731283) 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, 3455212 + ... + 3455217.

It is an arithmetic number, because the mean of its divisors is an integer number (6910430).

Almost surely, 2^20731287 is an apocalyptic number.

20731287 is a deficient number, since it is larger than the sum of its proper divisors (6910433).

20731287 is an equidigital number, since it uses as much as digits as its factorization.

20731287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6910432.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 20731287 is about 4553.1623076714. The cubic root of 20731287 is about 274.7106024450.

Adding to 20731287 its reverse (78213702), we get a palindrome (98944989).

The spelling of 20731287 in words is "twenty million, seven hundred thirty-one thousand, two hundred eighty-seven".