21305516 has 12 divisors (see below), whose sum is σ = 37317840. Its totient is φ = 10643280.

The previous prime is 21305513. The next prime is 21305533. The reversal of 21305516 is 61550312.

It is a junction number, because it is equal to n+sod(n) for n = 21305491 and 21305500.

It is not an unprimeable number, because it can be changed into a prime (21305513) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5870 + ... + 8778.

It is an arithmetic number, because the mean of its divisors is an integer number (3109820).

Almost surely, 2^21305516 is an apocalyptic number.

It is an amenable number.

21305516 is a deficient number, since it is larger than the sum of its proper divisors (16012324).

21305516 is a wasteful number, since it uses less digits than its factorization.

21305516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4744 (or 4742 counting only the distinct ones).

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21305516 is about 4615.7898565684. The cubic root of 21305516 is about 277.2239106716.

Adding to 21305516 its reverse (61550312), we get a palindrome (82855828).

The spelling of 21305516 in words is "twenty-one million, three hundred five thousand, five hundred sixteen".