21103281 has 32 divisors (see below), whose sum is σ = 33996800. Its totient is φ = 12888720.

The previous prime is 21103267. The next prime is 21103301. The reversal of 21103281 is 18230112.

It is not a de Polignac number, because 21103281 - 2⁵ = 21103249 is a prime.

It is a super-2 number, since 2×21103281² = 890696937929922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21103211) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15240 + ... + 16566.

It is an arithmetic number, because the mean of its divisors is an integer number (1062400).

Almost surely, 2^21103281 is an apocalyptic number.

It is an amenable number.

21103281 is a deficient number, since it is larger than the sum of its proper divisors (12893519).

21103281 is a wasteful number, since it uses less digits than its factorization.

21103281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1386 (or 1380 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21103281 is about 4593.8307543922. The cubic root of 21103281 is about 276.3439709517.

Adding to 21103281 its reverse (18230112), we get a palindrome (39333393).

The spelling of 21103281 in words is "twenty-one million, one hundred three thousand, two hundred eighty-one".