21170864 has 80 divisors (see below), whose sum is σ = 50830080. Its totient is φ = 8398080.

The previous prime is 21170857. The next prime is 21170881. The reversal of 21170864 is 46807112.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43229 + ... + 43715.

It is an arithmetic number, because the mean of its divisors is an integer number (635376).

Almost surely, 2^21170864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21170864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25415040).

21170864 is an abundant number, since it is smaller than the sum of its proper divisors (29659216).

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

21170864 is a wasteful number, since it uses less digits than its factorization.

21170864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538 (or 532 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 29.

The square root of 21170864 is about 4601.1807180331. The cubic root of 21170864 is about 276.6386526691.

Adding to 21170864 its reverse (46807112), we get a palindrome (67977976).

The spelling of 21170864 in words is "twenty-one million, one hundred seventy thousand, eight hundred sixty-four".