21290706 has 12 divisors (see below), whose sum is σ = 46129902. Its totient is φ = 7096896.

The previous prime is 21290701. The next prime is 21290729. The reversal of 21290706 is 60709212.

It can be written as a sum of positive squares in only one way, i.e., 21206025 + 84681 = 4605^2 + 291^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21290706.

It is not an unprimeable number, because it can be changed into a prime (21290701) 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 5 ways as a sum of consecutive naturals, for example, 591391 + ... + 591426.

Almost surely, 2^21290706 is an apocalyptic number.

21290706 is an abundant number, since it is smaller than the sum of its proper divisors (24839196).

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

21290706 is a wasteful number, since it uses less digits than its factorization.

21290706 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1182825 (or 1182822 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21290706 is about 4614.1853018707. The cubic root of 21290706 is about 277.1596606779.

Adding to 21290706 its reverse (60709212), we get a palindrome (81999918).

The spelling of 21290706 in words is "twenty-one million, two hundred ninety thousand, seven hundred six".