21005347 has 8 divisors (see below), whose sum is σ = 22963392. Its totient is φ = 19055400.

The previous prime is 21005339. The next prime is 21005363. The reversal of 21005347 is 74350012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21005347 - 2³ = 21005339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21008347) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4272 + ... + 7762.

It is an arithmetic number, because the mean of its divisors is an integer number (2870424).

Almost surely, 2^21005347 is an apocalyptic number.

21005347 is a deficient number, since it is larger than the sum of its proper divisors (1958045).

21005347 is a wasteful number, since it uses less digits than its factorization.

21005347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4049.

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21005347 is about 4583.1590633536. The cubic root of 21005347 is about 275.9158314726.

Adding to 21005347 its reverse (74350012), we get a palindrome (95355359).

It can be divided in two parts, 2100 and 5347, that added together give a palindrome (7447).

The spelling of 21005347 in words is "twenty-one million, five thousand, three hundred forty-seven".