21355224 has 64 divisors (see below), whose sum is σ = 60791040. Its totient is φ = 6188160.

The previous prime is 21355207. The next prime is 21355231. The reversal of 21355224 is 42255312.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a junction number, because it is equal to n+sod(n) for n = 21355194 and 21355203.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4314 + ... + 7830.

It is an arithmetic number, because the mean of its divisors is an integer number (949860).

Almost surely, 2^21355224 is an apocalyptic number.

21355224 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 21355224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30395520).

21355224 is an abundant number, since it is smaller than the sum of its proper divisors (39435816).

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

21355224 is a wasteful number, since it uses less digits than its factorization.

21355224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3560 (or 3556 counting only the distinct ones).

The product of its digits is 2400, while the sum is 24.

The square root of 21355224 is about 4621.1712800977. The cubic root of 21355224 is about 277.4393406899.

The spelling of 21355224 in words is "twenty-one million, three hundred fifty-five thousand, two hundred twenty-four".