21304643 has 4 divisors (see below), whose sum is σ = 22425960. Its totient is φ = 20183328.

The previous prime is 21304639. The next prime is 21304667. The reversal of 21304643 is 34640312.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21304643 - 2² = 21304639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21304603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 560630 + ... + 560667.

It is an arithmetic number, because the mean of its divisors is an integer number (5606490).

Almost surely, 2^21304643 is an apocalyptic number.

21304643 is a deficient number, since it is larger than the sum of its proper divisors (1121317).

21304643 is a wasteful number, since it uses less digits than its factorization.

21304643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1121316.

The product of its (nonzero) digits is 1728, while the sum is 23.

The square root of 21304643 is about 4615.6952889029. The cubic root of 21304643 is about 277.2201241752.

Adding to 21304643 its reverse (34640312), we get a palindrome (55944955).

The spelling of 21304643 in words is "twenty-one million, three hundred four thousand, six hundred forty-three".