21163680 has 240 divisors, whose sum is σ = 79035264. Its totient is φ = 5322240.

The previous prime is 21163643. The next prime is 21163687. The reversal of 21163680 is 8636112.

21163680 is a `hidden beast` number, since 21 + 1 + 636 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

It is a super-2 number, since 2×21163680² = 895802702284800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21163687) by changing a digit.

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 39 ways as a sum of consecutive naturals, for example, 298045 + ... + 298115.

Almost surely, 2^21163680 is an apocalyptic number.

21163680 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 21163680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39517632).

21163680 is an abundant number, since it is smaller than the sum of its proper divisors (57871584).

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

21163680 is a wasteful number, since it uses less digits than its factorization.

21163680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121 (or 104 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21163680 is about 4600.3999826102. The cubic root of 21163680 is about 276.6073581359.

Adding to 21163680 its reverse (8636112), we get a palindrome (29799792).

The spelling of 21163680 in words is "twenty-one million, one hundred sixty-three thousand, six hundred eighty".