21086281 has 2 divisors, whose sum is σ = 21086282. Its totient is φ = 21086280.

The previous prime is 21086279. The next prime is 21086287. The reversal of 21086281 is 18268012.

21086281 is nontrivially palindromic in base 15.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20793600 + 292681 = 4560^2 + 541^2 .

It is a cyclic number.

It is not a de Polignac number, because 21086281 - 2¹ = 21086279 is a prime.

It is a super-2 number, since 2×21086281² = 889262492821922, which contains 22 as substring.

Together with 21086279, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21086287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10543140 + 10543141.

It is an arithmetic number, because the mean of its divisors is an integer number (10543141).

Almost surely, 2^21086281 is an apocalyptic number.

It is an amenable number.

21086281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21086281 is an equidigital number, since it uses as much as digits as its factorization.

21086281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21086281 is about 4591.9800739986. The cubic root of 21086281 is about 276.2697469556.

The spelling of 21086281 in words is "twenty-one million, eighty-six thousand, two hundred eighty-one".