20999287 has 4 divisors (see below), whose sum is σ = 21051040. Its totient is φ = 20947536.

The previous prime is 20999273. The next prime is 20999317. The reversal of 20999287 is 78299902.

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 20999287 - 2⁷ = 20999159 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 (20999087) 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, 25263 + ... + 26080.

It is an arithmetic number, because the mean of its divisors is an integer number (5262760).

Almost surely, 2^20999287 is an apocalyptic number.

20999287 is a deficient number, since it is larger than the sum of its proper divisors (51753).

20999287 is an equidigital number, since it uses as much as digits as its factorization.

20999287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51752.

The product of its (nonzero) digits is 163296, while the sum is 46.

The square root of 20999287 is about 4582.4978996176. The cubic root of 20999287 is about 275.8892952013.

The spelling of 20999287 in words is "twenty million, nine hundred ninety-nine thousand, two hundred eighty-seven".