21700224 has 320 divisors, whose sum is σ = 82938240. Its totient is φ = 5474304.

The previous prime is 21700219. The next prime is 21700243. The reversal of 21700224 is 42200712.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21700197 and 21700206.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 943477 + ... + 943499.

It is an arithmetic number, because the mean of its divisors is an integer number (259182).

Almost surely, 2^21700224 is an apocalyptic number.

21700224 is a gapful number since it is divisible by the number (24) 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 21700224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41469120).

21700224 is an abundant number, since it is smaller than the sum of its proper divisors (61238016).

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

21700224 is a wasteful number, since it uses less digits than its factorization.

21700224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69 (or 48 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 21700224 is about 4658.3499224511. The cubic root of 21700224 is about 278.9254049622.

Adding to 21700224 its reverse (42200712), we get a palindrome (63900936).

The spelling of 21700224 in words is "twenty-one million, seven hundred thousand, two hundred twenty-four".