21305512 has 8 divisors (see below), whose sum is σ = 39947850. Its totient is φ = 10652752.

The previous prime is 21305507. The next prime is 21305513. The reversal of 21305512 is 21550312.

It can be written as a sum of positive squares in only one way, i.e., 20484676 + 820836 = 4526^2 + 906^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21305512.

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 as a sum of consecutive naturals, namely, 1331587 + ... + 1331602.

Almost surely, 2^21305512 is an apocalyptic number.

It is an amenable number.

21305512 is a deficient number, since it is larger than the sum of its proper divisors (18642338).

21305512 is a wasteful number, since it uses less digits than its factorization.

21305512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2663195 (or 2663191 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21305512 is about 4615.7894232731. The cubic root of 21305512 is about 277.2238933225.

Adding to 21305512 its reverse (21550312), we get a palindrome (42855824).

The spelling of 21305512 in words is "twenty-one million, three hundred five thousand, five hundred twelve".