21461665 has 8 divisors (see below), whose sum is σ = 26450280. Its totient is φ = 16705152.

The previous prime is 21461647. The next prime is 21461669. The reversal of 21461665 is 56616412.

It can be written as a sum of positive squares in 4 ways, for example, as 1827904 + 19633761 = 1352^2 + 4431^2 .

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 21461665 - 2¹⁷ = 21330593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21461669) 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, 57820 + ... + 58189.

It is an arithmetic number, because the mean of its divisors is an integer number (3306285).

Almost surely, 2^21461665 is an apocalyptic number.

It is an amenable number.

21461665 is a deficient number, since it is larger than the sum of its proper divisors (4988615).

21461665 is a wasteful number, since it uses less digits than its factorization.

21461665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116051.

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

The square root of 21461665 is about 4632.6736340908. The cubic root of 21461665 is about 277.8995246171.

The spelling of 21461665 in words is "twenty-one million, four hundred sixty-one thousand, six hundred sixty-five".