21287143 has 2 divisors, whose sum is σ = 21287144. Its totient is φ = 21287142.

The previous prime is 21287137. The next prime is 21287209. The reversal of 21287143 is 34178212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21287143 - 2¹⁷ = 21156071 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21287243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10643571 + 10643572.

It is an arithmetic number, because the mean of its divisors is an integer number (10643572).

Almost surely, 2^21287143 is an apocalyptic number.

21287143 is a deficient number, since it is larger than the sum of its proper divisors (1).

21287143 is an equidigital number, since it uses as much as digits as its factorization.

21287143 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 21287143 is about 4613.7991937231. The cubic root of 21287143 is about 277.1441989241.

The spelling of 21287143 in words is "twenty-one million, two hundred eighty-seven thousand, one hundred forty-three".