21724371 has 6 divisors (see below), whose sum is σ = 31379660. Its totient is φ = 14482908.

The previous prime is 21724369. The next prime is 21724379. The reversal of 21724371 is 17342712.

It is a happy number.

It is not a de Polignac number, because 21724371 - 2¹ = 21724369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21724379) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1206901 + ... + 1206918.

Almost surely, 2^21724371 is an apocalyptic number.

21724371 is a deficient number, since it is larger than the sum of its proper divisors (9655289).

21724371 is a wasteful number, since it uses less digits than its factorization.

21724371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2413825 (or 2413822 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 21724371 is about 4660.9409994120. The cubic root of 21724371 is about 279.0288250174.

The spelling of 21724371 in words is "twenty-one million, seven hundred twenty-four thousand, three hundred seventy-one".