21710281 has 2 divisors, whose sum is σ = 21710282. Its totient is φ = 21710280.

The previous prime is 21710267. The next prime is 21710317. The reversal of 21710281 is 18201712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21013056 + 697225 = 4584^2 + 835^2 .

It is a cyclic number.

It is not a de Polignac number, because 21710281 - 2⁷ = 21710153 is a prime.

It is a super-2 number, since 2×21710281² = 942672602197922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21710201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10855140 + 10855141.

It is an arithmetic number, because the mean of its divisors is an integer number (10855141).

Almost surely, 2^21710281 is an apocalyptic number.

It is an amenable number.

21710281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21710281 is an equidigital number, since it uses as much as digits as its factorization.

21710281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21710281 is about 4659.4292568940. The cubic root of 21710281 is about 278.9684877673.

Adding to 21710281 its reverse (18201712), we get a palindrome (39911993).

The spelling of 21710281 in words is "twenty-one million, seven hundred ten thousand, two hundred eighty-one".