21650281 has 2 divisors, whose sum is σ = 21650282. Its totient is φ = 21650280.

The previous prime is 21650263. The next prime is 21650287. The reversal of 21650281 is 18205612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18705625 + 2944656 = 4325^2 + 1716^2 .

It is a cyclic number.

It is not a de Polignac number, because 21650281 - 2⁵ = 21650249 is a prime.

It is a super-2 number, since 2×21650281² = 937469334757922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21650287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825140 + 10825141.

It is an arithmetic number, because the mean of its divisors is an integer number (10825141).

Almost surely, 2^21650281 is an apocalyptic number.

It is an amenable number.

21650281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21650281 is an equidigital number, since it uses as much as digits as its factorization.

21650281 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21650281 is about 4652.9862454127. The cubic root of 21650281 is about 278.7112586000.

Adding to 21650281 its reverse (18205612), we get a palindrome (39855893).

The spelling of 21650281 in words is "twenty-one million, six hundred fifty thousand, two hundred eighty-one".