21043660 has 48 divisors (see below), whose sum is σ = 49406112. Its totient is φ = 7462400.

The previous prime is 21043613. The next prime is 21043661. The reversal of 21043660 is 6634012.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is not an unprimeable number, because it can be changed into a prime (21043661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7854 + ... + 10186.

It is an arithmetic number, because the mean of its divisors is an integer number (1029294).

Almost surely, 2^21043660 is an apocalyptic number.

21043660 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 21043660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24703056).

21043660 is an abundant number, since it is smaller than the sum of its proper divisors (28362452).

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

21043660 is a wasteful number, since it uses less digits than its factorization.

21043660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2394 (or 2392 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 22.

The square root of 21043660 is about 4587.3369180822. The cubic root of 21043660 is about 276.0834831125.

Adding to 21043660 its reverse (6634012), we get a palindrome (27677672).

The spelling of 21043660 in words is "twenty-one million, forty-three thousand, six hundred sixty".