21281706 has 24 divisors (see below), whose sum is σ = 47236644. Its totient is φ = 6920640.

The previous prime is 21281683. The next prime is 21281707. The reversal of 21281706 is 60718212.

It can be written as a sum of positive squares in 2 ways, for example, as 20331081 + 950625 = 4509^2 + 975^2 .

It is a super-2 number, since 2×21281706² = 905822020540872, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21281706.

It is not an unprimeable number, because it can be changed into a prime (21281707) 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 in 11 ways as a sum of consecutive naturals, for example, 13681 + ... + 15156.

Almost surely, 2^21281706 is an apocalyptic number.

21281706 is an abundant number, since it is smaller than the sum of its proper divisors (25954938).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21281706 is a wasteful number, since it uses less digits than its factorization.

21281706 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28886 (or 28883 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21281706 is about 4613.2099453634. The cubic root of 21281706 is about 277.1206015612.

Adding to 21281706 its reverse (60718212), we get a palindrome (81999918).

It can be divided in two parts, 212 and 81706, that added together give a palindrome (81918).

The spelling of 21281706 in words is "twenty-one million, two hundred eighty-one thousand, seven hundred six".