21306680 has 32 divisors (see below), whose sum is σ = 48232800. Its totient is φ = 8470656.

The previous prime is 21306617. The next prime is 21306707. The reversal of 21306680 is 8660312.

It is a super-2 number, since 2×21306680² = 907949225244800, which contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 5381 + ... + 8459.

It is an arithmetic number, because the mean of its divisors is an integer number (1507275).

Almost surely, 2^21306680 is an apocalyptic number.

21306680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21306680 is an abundant number, since it is smaller than the sum of its proper divisors (26926120).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21306680 is a wasteful number, since it uses less digits than its factorization.

21306680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3263 (or 3259 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21306680 is about 4615.9159437754. The cubic root of 21306680 is about 277.2289591726.

Adding to 21306680 its reverse (8660312), we get a palindrome (29966992).

The spelling of 21306680 in words is "twenty-one million, three hundred six thousand, six hundred eighty".