21361615 has 16 divisors (see below), whose sum is σ = 28649376. Its totient is φ = 15155200.

The previous prime is 21361609. The next prime is 21361619. The reversal of 21361615 is 51616312.

It is a de Polignac number, because none of the positive numbers 2^k-21361615 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21361615.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21361619) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2482 + ... + 6991.

It is an arithmetic number, because the mean of its divisors is an integer number (1790586).

Almost surely, 2^21361615 is an apocalyptic number.

21361615 is a deficient number, since it is larger than the sum of its proper divisors (7287761).

21361615 is a wasteful number, since it uses less digits than its factorization.

21361615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9530.

The product of its digits is 1080, while the sum is 25.

The square root of 21361615 is about 4621.8627197268. The cubic root of 21361615 is about 277.4670144490.

Adding to 21361615 its reverse (51616312), we get a palindrome (72977927).

The spelling of 21361615 in words is "twenty-one million, three hundred sixty-one thousand, six hundred fifteen".