21315615 has 8 divisors (see below), whose sum is σ = 34105008. Its totient is φ = 11368320.

The previous prime is 21315611. The next prime is 21315643. The reversal of 21315615 is 51651312.

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

It is not a de Polignac number, because 21315615 - 2² = 21315611 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315611) 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, 710506 + ... + 710535.

It is an arithmetic number, because the mean of its divisors is an integer number (4263126).

Almost surely, 2^21315615 is an apocalyptic number.

21315615 is a deficient number, since it is larger than the sum of its proper divisors (12789393).

21315615 is a wasteful number, since it uses less digits than its factorization.

21315615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1421049.

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

The square root of 21315615 is about 4616.8836892432. The cubic root of 21315615 is about 277.2677059347.

Adding to 21315615 its reverse (51651312), we get a palindrome (72966927).

The spelling of 21315615 in words is "twenty-one million, three hundred fifteen thousand, six hundred fifteen".