21242665 has 16 divisors (see below), whose sum is σ = 27345600. Its totient is φ = 15792192.

The previous prime is 21242659. The next prime is 21242681. The reversal of 21242665 is 56624212.

It is not a de Polignac number, because 21242665 - 2⁹ = 21242153 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2926 + ... + 7144.

It is an arithmetic number, because the mean of its divisors is an integer number (1709100).

Almost surely, 2^21242665 is an apocalyptic number.

It is an amenable number.

21242665 is a deficient number, since it is larger than the sum of its proper divisors (6102935).

21242665 is a wasteful number, since it uses less digits than its factorization.

21242665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4296.

The product of its digits is 5760, while the sum is 28.

The square root of 21242665 is about 4608.9765675256. The cubic root of 21242665 is about 276.9510398421.

Adding to 21242665 its reverse (56624212), we get a palindrome (77866877).

The spelling of 21242665 in words is "twenty-one million, two hundred forty-two thousand, six hundred sixty-five".