21724126 has 4 divisors (see below), whose sum is σ = 32586192. Its totient is φ = 10862062.

The previous prime is 21724111. The next prime is 21724133. The reversal of 21724126 is 62142712.

It is a semiprime because it is the product of two primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21724126.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5431030 + ... + 5431033.

It is an arithmetic number, because the mean of its divisors is an integer number (8146548).

Almost surely, 2^21724126 is an apocalyptic number.

21724126 is a deficient number, since it is larger than the sum of its proper divisors (10862066).

21724126 is a wasteful number, since it uses less digits than its factorization.

21724126 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10862065.

The product of its digits is 1344, while the sum is 25.

The square root of 21724126 is about 4660.9147170915. The cubic root of 21724126 is about 279.0277760830.

Adding to 21724126 its reverse (62142712), we get a palindrome (83866838).

The spelling of 21724126 in words is "twenty-one million, seven hundred twenty-four thousand, one hundred twenty-six".