21308315 has 32 divisors (see below), whose sum is σ = 30965760. Its totient is φ = 13766400.

The previous prime is 21308311. The next prime is 21308347. The reversal of 21308315 is 51380312.

It is not a de Polignac number, because 21308315 - 2² = 21308311 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21308311) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 44246 + ... + 44724.

It is an arithmetic number, because the mean of its divisors is an integer number (967680).

Almost surely, 2^21308315 is an apocalyptic number.

21308315 is a deficient number, since it is larger than the sum of its proper divisors (9657445).

21308315 is a wasteful number, since it uses less digits than its factorization.

21308315 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 563.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21308315 is about 4616.0930449895. The cubic root of 21308315 is about 277.2360501844.

Adding to 21308315 its reverse (51380312), we get a palindrome (72688627).

The spelling of 21308315 in words is "twenty-one million, three hundred eight thousand, three hundred fifteen".