21215347 has 4 divisors (see below), whose sum is σ = 21231000. Its totient is φ = 21199696.

The previous prime is 21215339. The next prime is 21215399. The reversal of 21215347 is 74351212.

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 21215347 - 2³ = 21215339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21215147) 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, 5578 + ... + 8575.

It is an arithmetic number, because the mean of its divisors is an integer number (5307750).

Almost surely, 2^21215347 is an apocalyptic number.

21215347 is a deficient number, since it is larger than the sum of its proper divisors (15653).

21215347 is a wasteful number, since it uses less digits than its factorization.

21215347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15652.

The product of its digits is 1680, while the sum is 25.

The square root of 21215347 is about 4606.0120494849. The cubic root of 21215347 is about 276.8322695277.

Adding to 21215347 its reverse (74351212), we get a palindrome (95566559).

The spelling of 21215347 in words is "twenty-one million, two hundred fifteen thousand, three hundred forty-seven".