21406516 has 12 divisors (see below), whose sum is σ = 37658880. Its totient is φ = 10646840.

The previous prime is 21406507. The next prime is 21406529. The reversal of 21406516 is 61560412.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13246 + ... + 14773.

It is an arithmetic number, because the mean of its divisors is an integer number (3138240).

Almost surely, 2^21406516 is an apocalyptic number.

It is an amenable number.

21406516 is a deficient number, since it is larger than the sum of its proper divisors (16252364).

21406516 is a wasteful number, since it uses less digits than its factorization.

21406516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28214 (or 28212 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21406516 is about 4626.7176270008. The cubic root of 21406516 is about 277.6612854584.

Adding to 21406516 its reverse (61560412), we get a palindrome (82966928).

The spelling of 21406516 in words is "twenty-one million, four hundred six thousand, five hundred sixteen".