21680064 has 168 divisors, whose sum is σ = 75021440. Its totient is φ = 5847552.

The previous prime is 21680059. The next prime is 21680069. The reversal of 21680064 is 46008612.

It is an interprime number because it is at equal distance from previous prime (21680059) and next prime (21680069).

It is a tau number, because it is divible by the number of its divisors (168).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680069) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76467 + ... + 76749.

Almost surely, 2^21680064 is an apocalyptic number.

21680064 is a gapful number since it is divisible by the number (24) 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 21680064, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37510720).

21680064 is an abundant number, since it is smaller than the sum of its proper divisors (53341376).

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

21680064 is a wasteful number, since it uses less digits than its factorization.

21680064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 327 (or 314 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 21680064 is about 4656.1855633125. The cubic root of 21680064 is about 278.8390021920.

Adding to 21680064 its reverse (46008612), we get a palindrome (67688676).

The spelling of 21680064 in words is "twenty-one million, six hundred eighty thousand, sixty-four".