21323561 has 8 divisors (see below), whose sum is σ = 24594240. Its totient is φ = 18109008.

The previous prime is 21323531. The next prime is 21323591. The reversal of 21323561 is 16532312.

It is an interprime number because it is at equal distance from previous prime (21323531) and next prime (21323591).

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 21323561 - 2²² = 17129257 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21323521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13211 + ... + 14736.

It is an arithmetic number, because the mean of its divisors is an integer number (3074280).

Almost surely, 2^21323561 is an apocalyptic number.

It is an amenable number.

21323561 is a deficient number, since it is larger than the sum of its proper divisors (3270679).

21323561 is a wasteful number, since it uses less digits than its factorization.

21323561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28063.

The product of its digits is 1080, while the sum is 23.

The square root of 21323561 is about 4617.7441462255. The cubic root of 21323561 is about 277.3021547880.

Adding to 21323561 its reverse (16532312), we get a palindrome (37855873).

The spelling of 21323561 in words is "twenty-one million, three hundred twenty-three thousand, five hundred sixty-one".