21542065 has 4 divisors (see below), whose sum is σ = 25850484. Its totient is φ = 17233648.

The previous prime is 21542063. The next prime is 21542071. The reversal of 21542065 is 56024512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2383936 + 19158129 = 1544^2 + 4377^2 .

It is a cyclic number.

It is not a de Polignac number, because 21542065 - 2¹ = 21542063 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21542063) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2154202 + ... + 2154211.

It is an arithmetic number, because the mean of its divisors is an integer number (6462621).

Almost surely, 2^21542065 is an apocalyptic number.

It is an amenable number.

21542065 is a deficient number, since it is larger than the sum of its proper divisors (4308419).

21542065 is an equidigital number, since it uses as much as digits as its factorization.

21542065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4308418.

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 21542065 is about 4641.3430168433. The cubic root of 21542065 is about 278.2461159152.

Adding to 21542065 its reverse (56024512), we get a palindrome (77566577).

The spelling of 21542065 in words is "twenty-one million, five hundred forty-two thousand, sixty-five".