21317664 has 24 divisors (see below), whose sum is σ = 55959120. Its totient is φ = 7105856.

The previous prime is 21317651. The next prime is 21317669. The reversal of 21317664 is 46671312.

It is a tau number, because it is divible by the number of its divisors (24).

It is not an unprimeable number, because it can be changed into a prime (21317669) 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 3 ways as a sum of consecutive naturals, for example, 110934 + ... + 111125.

It is an arithmetic number, because the mean of its divisors is an integer number (2331630).

Almost surely, 2^21317664 is an apocalyptic number.

21317664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21317664 is an abundant number, since it is smaller than the sum of its proper divisors (34641456).

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

21317664 is a wasteful number, since it uses less digits than its factorization.

21317664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222072 (or 222064 counting only the distinct ones).

The product of its digits is 6048, while the sum is 30.

The square root of 21317664 is about 4617.1055868368. The cubic root of 21317664 is about 277.2765899277.

Adding to 21317664 its reverse (46671312), we get a palindrome (67988976).

The spelling of 21317664 in words is "twenty-one million, three hundred seventeen thousand, six hundred sixty-four".