21724937 has 8 divisors (see below), whose sum is σ = 23446920. Its totient is φ = 20010240.

The previous prime is 21724931. The next prime is 21724939. The reversal of 21724937 is 73942712.

It can be written as a sum of positive squares in 4 ways, for example, as 3200521 + 18524416 = 1789^2 + 4304^2 .

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 21724937 - 2¹⁰ = 21723913 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21724897 and 21724906.

It is not an unprimeable number, because it can be changed into a prime (21724931) 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, 5489 + ... + 8577.

It is an arithmetic number, because the mean of its divisors is an integer number (2930865).

Almost surely, 2^21724937 is an apocalyptic number.

It is an amenable number.

21724937 is a deficient number, since it is larger than the sum of its proper divisors (1721983).

21724937 is a wasteful number, since it uses less digits than its factorization.

21724937 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3643.

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

The square root of 21724937 is about 4661.0017163696. The cubic root of 21724937 is about 279.0312482397.

The spelling of 21724937 in words is "twenty-one million, seven hundred twenty-four thousand, nine hundred thirty-seven".