21668400 has 180 divisors, whose sum is σ = 81154528. Its totient is φ = 5322240.

The previous prime is 21668389. The next prime is 21668401. The reversal of 21668400 is 486612.

It is a tau number, because it is divible by the number of its divisors (180).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21668401) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 46569 + ... + 47031.

Almost surely, 2^21668400 is an apocalyptic number.

21668400 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 21668400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40577264).

21668400 is an abundant number, since it is smaller than the sum of its proper divisors (59486128).

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

21668400 is a wasteful number, since it uses less digits than its factorization.

21668400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500 (or 486 counting only the distinct ones).

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

The square root of 21668400 is about 4654.9328673999. The cubic root of 21668400 is about 278.7889875555.

The spelling of 21668400 in words is "twenty-one million, six hundred sixty-eight thousand, four hundred".