21071424 has 84 divisors (see below), whose sum is σ = 61348112. Its totient is φ = 6378240.

The previous prime is 21071423. The next prime is 21071447. The reversal of 21071424 is 42417012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21071424.

It is not an unprimeable number, because it can be changed into a prime (21071423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22779 + ... + 23685.

Almost surely, 2^21071424 is an apocalyptic number.

21071424 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 21071424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30674056).

21071424 is an abundant number, since it is smaller than the sum of its proper divisors (40276688).

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

21071424 is a wasteful number, since it uses less digits than its factorization.

21071424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 944 (or 923 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21071424 is about 4590.3620772222. The cubic root of 21071424 is about 276.2048468751.

Adding to 21071424 its reverse (42417012), we get a palindrome (63488436).

The spelling of 21071424 in words is "twenty-one million, seventy-one thousand, four hundred twenty-four".