21168840 has 256 divisors, whose sum is σ = 82944000. Its totient is φ = 4193280.

The previous prime is 21168827. The next prime is 21168871. The reversal of 21168840 is 4886112.

21168840 = T₆₃ + T₆₄ + ... + T₅₀₂.

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

It is a junction number, because it is equal to n+sod(n) for n = 21168798 and 21168807.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 267921 + ... + 267999.

It is an arithmetic number, because the mean of its divisors is an integer number (324000).

Almost surely, 2^21168840 is an apocalyptic number.

21168840 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 21168840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41472000).

21168840 is an abundant number, since it is smaller than the sum of its proper divisors (61775160).

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

21168840 is a wasteful number, since it uses less digits than its factorization.

21168840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140 (or 136 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21168840 is about 4600.9607692307. The cubic root of 21168840 is about 276.6298365515.

It can be divided in two parts, 21 and 168840, that added together give a palindrome (168861).

The spelling of 21168840 in words is "twenty-one million, one hundred sixty-eight thousand, eight hundred forty".