21401224 has 48 divisors (see below), whose sum is σ = 45290700. Its totient is φ = 9423744.

The previous prime is 21401203. The next prime is 21401251. The reversal of 21401224 is 42210412.

It can be written as a sum of positive squares in 2 ways, for example, as 19096900 + 2304324 = 4370^2 + 1518^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21401198 and 21401207.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 54822 + ... + 55210.

Almost surely, 2^21401224 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 21401224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22645350).

21401224 is an abundant number, since it is smaller than the sum of its proper divisors (23889476).

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

21401224 is a wasteful number, since it uses less digits than its factorization.

21401224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 454 (or 427 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21401224 is about 4626.1456959331. The cubic root of 21401224 is about 277.6384029456.

Adding to 21401224 its reverse (42210412), we get a palindrome (63611636).

It can be divided in two parts, 2140 and 1224, that added together give a square (3364 = 58²).

The spelling of 21401224 in words is "twenty-one million, four hundred one thousand, two hundred twenty-four".