21315315 has 32 divisors (see below), whose sum is σ = 39891456. Its totient is φ = 9515520.

The previous prime is 21315289. The next prime is 21315341. The reversal of 21315315 is 51351312.

It is an interprime number because it is at equal distance from previous prime (21315289) and next prime (21315341).

It is not a de Polignac number, because 21315315 - 2⁶ = 21315251 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21315291 and 21315300.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2155 + ... + 6875.

It is an arithmetic number, because the mean of its divisors is an integer number (1246608).

Almost surely, 2^21315315 is an apocalyptic number.

21315315 is a deficient number, since it is larger than the sum of its proper divisors (18576141).

21315315 is a wasteful number, since it uses less digits than its factorization.

21315315 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4779.

The product of its digits is 450, while the sum is 21.

The square root of 21315315 is about 4616.8511996814. The cubic root of 21315315 is about 277.2664051558.

Adding to 21315315 its reverse (51351312), we get a palindrome (72666627).

The spelling of 21315315 in words is "twenty-one million, three hundred fifteen thousand, three hundred fifteen".