21405316 has 6 divisors (see below), whose sum is σ = 37459310. Its totient is φ = 10702656.

The previous prime is 21405313. The next prime is 21405337. The reversal of 21405316 is 61350412.

It can be written as a sum of positive squares in only one way, i.e., 19766916 + 1638400 = 4446^2 + 1280^2 .

It is not an unprimeable number, because it can be changed into a prime (21405313) by changing a digit.

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 as a sum of consecutive naturals, namely, 2675661 + ... + 2675668.

Almost surely, 2^21405316 is an apocalyptic number.

It is an amenable number.

21405316 is a deficient number, since it is larger than the sum of its proper divisors (16053994).

21405316 is a wasteful number, since it uses less digits than its factorization.

21405316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5351333 (or 5351331 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21405316 is about 4626.5879436146. The cubic root of 21405316 is about 277.6560970106.

Adding to 21405316 its reverse (61350412), we get a palindrome (82755728).

The spelling of 21405316 in words is "twenty-one million, four hundred five thousand, three hundred sixteen".