21516243 has 12 divisors (see below), whose sum is σ = 33372360. Its totient is φ = 12294912.

The previous prime is 21516241. The next prime is 21516259. The reversal of 21516243 is 34261512.

It is not a de Polignac number, because 21516243 - 2¹ = 21516241 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21516241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 73038 + ... + 73331.

It is an arithmetic number, because the mean of its divisors is an integer number (2781030).

Almost surely, 2^21516243 is an apocalyptic number.

21516243 is a deficient number, since it is larger than the sum of its proper divisors (11856117).

21516243 is a wasteful number, since it uses less digits than its factorization.

21516243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146386 (or 146379 counting only the distinct ones).

The product of its digits is 1440, while the sum is 24.

The square root of 21516243 is about 4638.5604447932. The cubic root of 21516243 is about 278.1348956291.

Adding to 21516243 its reverse (34261512), we get a palindrome (55777755).

The spelling of 21516243 in words is "twenty-one million, five hundred sixteen thousand, two hundred forty-three".