21342816 has 72 divisors (see below), whose sum is σ = 66221064. Its totient is φ = 6466560.

The previous prime is 21342809. The next prime is 21342817. The reversal of 21342816 is 61824312.

It is a tau number, because it is divible by the number of its divisors (72).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21342816.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21342817) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 201 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (919737).

Almost surely, 2^21342816 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 21342816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33110532).

21342816 is an abundant number, since it is smaller than the sum of its proper divisors (44878248).

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

21342816 is a wasteful number, since it uses less digits than its factorization.

21342816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6764 (or 6753 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21342816 is about 4619.8285682480. The cubic root of 21342816 is about 277.3855968646.

It can be divided in two parts, 213428 and 16, that added together give a square (213444 = 462²).

The spelling of 21342816 in words is "twenty-one million, three hundred forty-two thousand, eight hundred sixteen".