21340447 has 4 divisors (see below), whose sum is σ = 21361480. Its totient is φ = 21319416.

The previous prime is 21340441. The next prime is 21340469. The reversal of 21340447 is 74404312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21340447 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21340441) 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, 8913 + ... + 11050.

It is an arithmetic number, because the mean of its divisors is an integer number (5340370).

Almost surely, 2^21340447 is an apocalyptic number.

21340447 is a deficient number, since it is larger than the sum of its proper divisors (21033).

21340447 is a wasteful number, since it uses less digits than its factorization.

21340447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21032.

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 21340447 is about 4619.5721663375. The cubic root of 21340447 is about 277.3753334456.

Adding to 21340447 its reverse (74404312), we get a palindrome (95744759).

The spelling of 21340447 in words is "twenty-one million, three hundred forty thousand, four hundred forty-seven".