21516315 has 8 divisors (see below), whose sum is σ = 34426128. Its totient is φ = 11475360.

The previous prime is 21516311. The next prime is 21516359. The reversal of 21516315 is 51361512.

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

It is not a de Polignac number, because 21516315 - 2² = 21516311 is a prime.

It is a super-2 number, since 2×21516315² = 925903622358450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21516311) 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, 717196 + ... + 717225.

It is an arithmetic number, because the mean of its divisors is an integer number (4303266).

Almost surely, 2^21516315 is an apocalyptic number.

21516315 is a deficient number, since it is larger than the sum of its proper divisors (12909813).

21516315 is a wasteful number, since it uses less digits than its factorization.

21516315 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1434429.

The product of its digits is 900, while the sum is 24.

The square root of 21516315 is about 4638.5682058152. The cubic root of 21516315 is about 278.1352058705.

Adding to 21516315 its reverse (51361512), we get a palindrome (72877827).

The spelling of 21516315 in words is "twenty-one million, five hundred sixteen thousand, three hundred fifteen".