21306512 has 10 divisors (see below), whose sum is σ = 41281398. Its totient is φ = 10653248.

The previous prime is 21306479. The next prime is 21306539. The reversal of 21306512 is 21560312.

It can be written as a sum of positive squares in only one way, i.e., 19044496 + 2262016 = 4364^2 + 1504^2 .

It is a super-2 number, since 2×21306512² = 907934907212288, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665813 + ... + 665844.

Almost surely, 2^21306512 is an apocalyptic number.

It is an amenable number.

21306512 is a deficient number, since it is larger than the sum of its proper divisors (19974886).

21306512 is a wasteful number, since it uses less digits than its factorization.

21306512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1331665 (or 1331659 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21306512 is about 4615.8977458345. The cubic root of 21306512 is about 277.2282305343.

Adding to 21306512 its reverse (21560312), we get a palindrome (42866824).

The spelling of 21306512 in words is "twenty-one million, three hundred six thousand, five hundred twelve".