21315680 has 48 divisors (see below), whose sum is σ = 50803200. Its totient is φ = 8451072.

The previous prime is 21315661. The next prime is 21315689. The reversal of 21315680 is 8651312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19796 + ... + 20844.

It is an arithmetic number, because the mean of its divisors is an integer number (1058400).

Almost surely, 2^21315680 is an apocalyptic number.

21315680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25401600).

21315680 is an abundant number, since it is smaller than the sum of its proper divisors (29487520).

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

21315680 is a wasteful number, since it uses less digits than its factorization.

21315680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1191 (or 1183 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21315680 is about 4616.8907286181. The cubic root of 21315680 is about 277.2679877685.

Adding to 21315680 its reverse (8651312), we get a palindrome (29966992).

The spelling of 21315680 in words is "twenty-one million, three hundred fifteen thousand, six hundred eighty".