21724397 has 8 divisors (see below), whose sum is σ = 23400960. Its totient is φ = 20108880.

The previous prime is 21724379. The next prime is 21724399. The reversal of 21724397 is 79342712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21724397 - 2⁶ = 21724333 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724399) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14522 + ... + 15947.

It is an arithmetic number, because the mean of its divisors is an integer number (2925120).

Almost surely, 2^21724397 is an apocalyptic number.

It is an amenable number.

21724397 is a deficient number, since it is larger than the sum of its proper divisors (1676563).

21724397 is a wasteful number, since it uses less digits than its factorization.

21724397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30523.

The product of its digits is 21168, while the sum is 35.

The square root of 21724397 is about 4660.9437885476. The cubic root of 21724397 is about 279.0289363324.

The spelling of 21724397 in words is "twenty-one million, seven hundred twenty-four thousand, three hundred ninety-seven".