21168660 has 96 divisors (see below), whose sum is σ = 64512000. Its totient is φ = 5166720.

The previous prime is 21168649. The next prime is 21168701. The reversal of 21168660 is 6686112.

It is a super-2 number, since 2×21168660² = 896224332391200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 35041 + ... + 35639.

It is an arithmetic number, because the mean of its divisors is an integer number (672000).

Almost surely, 2^21168660 is an apocalyptic number.

21168660 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 21168660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32256000).

21168660 is an abundant number, since it is smaller than the sum of its proper divisors (43343340).

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

21168660 is a wasteful number, since it uses less digits than its factorization.

21168660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 661 (or 659 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21168660 is about 4600.9412080573. The cubic root of 21168660 is about 276.6290524822.

The spelling of 21168660 in words is "twenty-one million, one hundred sixty-eight thousand, six hundred sixty".