21665461 has 8 divisors (see below), whose sum is σ = 22356920. Its totient is φ = 20979648.

The previous prime is 21665401. The next prime is 21665473. The reversal of 21665461 is 16456612.

It can be written as a sum of positive squares in 4 ways, for example, as 12117361 + 9548100 = 3481^2 + 3090^2 .

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 21665461 - 2¹¹ = 21663413 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 (21665401) 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, 7195 + ... + 9751.

It is an arithmetic number, because the mean of its divisors is an integer number (2794615).

Almost surely, 2^21665461 is an apocalyptic number.

It is an amenable number.

21665461 is a deficient number, since it is larger than the sum of its proper divisors (691459).

21665461 is a wasteful number, since it uses less digits than its factorization.

21665461 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2823.

The product of its digits is 8640, while the sum is 31.

The square root of 21665461 is about 4654.6171700796. The cubic root of 21665461 is about 278.7763824426.

The spelling of 21665461 in words is "twenty-one million, six hundred sixty-five thousand, four hundred sixty-one".