21724030 has 32 divisors (see below), whose sum is σ = 42134400. Its totient is φ = 8037792.

The previous prime is 21724019. The next prime is 21724037. The reversal of 21724030 is 3042712.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a junction number, because it is equal to n+sod(n) for n = 21723989 and 21724007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724037) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6841 + ... + 9499.

It is an arithmetic number, because the mean of its divisors is an integer number (1316700).

Almost surely, 2^21724030 is an apocalyptic number.

21724030 is a deficient number, since it is larger than the sum of its proper divisors (20410370).

21724030 is a wasteful number, since it uses less digits than its factorization.

21724030 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2728.

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

The square root of 21724030 is about 4660.9044186724. The cubic root of 21724030 is about 279.0273650698.

Adding to 21724030 its reverse (3042712), we get a palindrome (24766742).

The spelling of 21724030 in words is "twenty-one million, seven hundred twenty-four thousand, thirty".