21003724 has 12 divisors (see below), whose sum is σ = 42007504. Its totient is φ = 9001584.

The previous prime is 21003713. The next prime is 21003727. The reversal of 21003724 is 42730012.

21003724 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21003727) 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, 375039 + ... + 375094.

Almost surely, 2^21003724 is an apocalyptic number.

It is an amenable number.

21003724 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21003724 is a wasteful number, since it uses less digits than its factorization.

21003724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750144 (or 750142 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21003724 is about 4582.9819986555. The cubic root of 21003724 is about 275.9087249816.

Adding to 21003724 its reverse (42730012), we get a palindrome (63733736).

The spelling of 21003724 in words is "twenty-one million, three thousand, seven hundred twenty-four".