21001424 has 20 divisors (see below), whose sum is σ = 40817700. Its totient is φ = 10467840.

The previous prime is 21001417. The next prime is 21001429. The reversal of 21001424 is 42410012.

It can be written as a sum of positive squares in 2 ways, for example, as 12475024 + 8526400 = 3532^2 + 2920^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21001399 and 21001408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001429) 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, 3704 + ... + 7464.

It is an arithmetic number, because the mean of its divisors is an integer number (2040885).

Almost surely, 2^21001424 is an apocalyptic number.

It is an amenable number.

21001424 is a deficient number, since it is larger than the sum of its proper divisors (19816276).

21001424 is a wasteful number, since it uses less digits than its factorization.

21001424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4118 (or 4112 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21001424 is about 4582.7310634599. The cubic root of 21001424 is about 275.8986535417.

Adding to 21001424 its reverse (42410012), we get a palindrome (63411436).

The spelling of 21001424 in words is "twenty-one million, one thousand, four hundred twenty-four".