21724061 has 4 divisors (see below), whose sum is σ = 21746400. Its totient is φ = 21701724.

The previous prime is 21724057. The next prime is 21724081. The reversal of 21724061 is 16042712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21724061 - 2² = 21724057 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9641 + ... + 11678.

It is an arithmetic number, because the mean of its divisors is an integer number (5436600).

Almost surely, 2^21724061 is an apocalyptic number.

It is an amenable number.

21724061 is a deficient number, since it is larger than the sum of its proper divisors (22339).

21724061 is a wasteful number, since it uses less digits than its factorization.

21724061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22338.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21724061 is about 4660.9077442061. The cubic root of 21724061 is about 279.0274977929.

Adding to 21724061 its reverse (16042712), we get a palindrome (37766773).

The spelling of 21724061 in words is "twenty-one million, seven hundred twenty-four thousand, sixty-one".