21284281 has 2 divisors, whose sum is σ = 21284282. Its totient is φ = 21284280.

The previous prime is 21284273. The next prime is 21284299. The reversal of 21284281 is 18248212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17640000 + 3644281 = 4200^2 + 1909^2 .

It is a cyclic number.

It is not a de Polignac number, because 21284281 - 2³ = 21284273 is a prime.

It is a super-2 number, since 2×21284281² = 906041235373922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21284251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10642140 + 10642141.

It is an arithmetic number, because the mean of its divisors is an integer number (10642141).

Almost surely, 2^21284281 is an apocalyptic number.

It is an amenable number.

21284281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21284281 is an equidigital number, since it uses as much as digits as its factorization.

21284281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2048, while the sum is 28.

The square root of 21284281 is about 4613.4890267562. The cubic root of 21284281 is about 277.1317779329.

The spelling of 21284281 in words is "twenty-one million, two hundred eighty-four thousand, two hundred eighty-one".