21345641 has 4 divisors (see below), whose sum is σ = 21369984. Its totient is φ = 21321300.

The previous prime is 21345637. The next prime is 21345703. The reversal of 21345641 is 14654312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21345641 - 2² = 21345637 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21345641.

It is not an unprimeable number, because it can be changed into a prime (21345241) 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 3 ways as a sum of consecutive naturals, for example, 10805 + ... + 12626.

It is an arithmetic number, because the mean of its divisors is an integer number (5342496).

Almost surely, 2^21345641 is an apocalyptic number.

It is an amenable number.

21345641 is a deficient number, since it is larger than the sum of its proper divisors (24343).

21345641 is an equidigital number, since it uses as much as digits as its factorization.

21345641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24342.

The product of its digits is 2880, while the sum is 26.

The square root of 21345641 is about 4620.1343054071. The cubic root of 21345641 is about 277.3978348583.

Adding to 21345641 its reverse (14654312), we get a palindrome (35999953).

It can be divided in two parts, 213 and 45641, that added together give a palindrome (45854).

The spelling of 21345641 in words is "twenty-one million, three hundred forty-five thousand, six hundred forty-one".