21378224 has 80 divisors (see below), whose sum is σ = 50806272. Its totient is φ = 8515584.

The previous prime is 21378223. The next prime is 21378229. The reversal of 21378224 is 42287312.

It is a super-2 number, since 2×21378224² = 914056922788352, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21378223) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 110672 + ... + 110864.

Almost surely, 2^21378224 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 21378224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25403136).

21378224 is an abundant number, since it is smaller than the sum of its proper divisors (29428048).

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

21378224 is a wasteful number, since it uses less digits than its factorization.

21378224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274 (or 268 counting only the distinct ones).

The product of its digits is 5376, while the sum is 29.

The square root of 21378224 is about 4623.6591569881. The cubic root of 21378224 is about 277.5389075117.

The spelling of 21378224 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred twenty-four".