21716864 has 64 divisors (see below), whose sum is σ = 48209280. Its totient is φ = 9676800.

The previous prime is 21716861. The next prime is 21716869. The reversal of 21716864 is 46861712.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716861) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 51374 + ... + 51794.

It is an arithmetic number, because the mean of its divisors is an integer number (753270).

Almost surely, 2^21716864 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 21716864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24104640).

21716864 is an abundant number, since it is smaller than the sum of its proper divisors (26492416).

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

21716864 is a wasteful number, since it uses less digits than its factorization.

21716864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 479 (or 467 counting only the distinct ones).

The product of its digits is 16128, while the sum is 35.

The square root of 21716864 is about 4660.1356203441. The cubic root of 21716864 is about 278.9966812296.

The spelling of 21716864 in words is "twenty-one million, seven hundred sixteen thousand, eight hundred sixty-four".