21000024 has 48 divisors (see below), whose sum is σ = 57142800. Its totient is φ = 6967104.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000024 is 42000012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18382 + ... + 19490.

It is an arithmetic number, because the mean of its divisors is an integer number (1190475).

Almost surely, 2^21000024 is an apocalyptic number.

21000024 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21000024 is an abundant number, since it is smaller than the sum of its proper divisors (36142776).

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

21000024 is a wasteful number, since it uses less digits than its factorization.

21000024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1384 (or 1377 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 21000024 is about 4582.5783135698. The cubic root of 21000024 is about 275.8925227399.

Adding to 21000024 its reverse (42000012), we get a palindrome (63000036).

The spelling of 21000024 in words is "twenty-one million, twenty-four", and thus it is an aban number.