21643315 has 8 divisors (see below), whose sum is σ = 26087760. Its totient is φ = 17237472.

The previous prime is 21643313. The next prime is 21643331. The reversal of 21643315 is 51334612.

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

It is not a de Polignac number, because 21643315 - 2¹ = 21643313 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21643315.

It is not an unprimeable number, because it can be changed into a prime (21643313) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8400 + ... + 10669.

It is an arithmetic number, because the mean of its divisors is an integer number (3260970).

Almost surely, 2^21643315 is an apocalyptic number.

21643315 is a deficient number, since it is larger than the sum of its proper divisors (4444445).

21643315 is a wasteful number, since it uses less digits than its factorization.

21643315 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19301.

The product of its digits is 2160, while the sum is 25.

The square root of 21643315 is about 4652.2376336554. The cubic root of 21643315 is about 278.6813635162.

Adding to 21643315 its reverse (51334612), we get a palindrome (72977927).

The spelling of 21643315 in words is "twenty-one million, six hundred forty-three thousand, three hundred fifteen".