21072424 has 16 divisors (see below), whose sum is σ = 39590100. Its totient is φ = 10515072.

The previous prime is 21072421. The next prime is 21072431. The reversal of 21072424 is 42427012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 15069924 + 6002500 = 3882^2 + 2450^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21072395 and 21072404.

It is not an unprimeable number, because it can be changed into a prime (21072421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2092 + ... + 6820.

Almost surely, 2^21072424 is an apocalyptic number.

It is an amenable number.

21072424 is a deficient number, since it is larger than the sum of its proper divisors (18517676).

21072424 is a wasteful number, since it uses less digits than its factorization.

21072424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5292 (or 5288 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21072424 is about 4590.4709997995. The cubic root of 21072424 is about 276.2092161491.

Adding to 21072424 its reverse (42427012), we get a palindrome (63499436).

The spelling of 21072424 in words is "twenty-one million, seventy-two thousand, four hundred twenty-four".