21516235 has 12 divisors (see below), whose sum is σ = 27959472. Its totient is φ = 15888288.

The previous prime is 21516233. The next prime is 21516241. The reversal of 21516235 is 53261512.

It is not a de Polignac number, because 21516235 - 2¹ = 21516233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21516233) 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, 11887 + ... + 13576.

It is an arithmetic number, because the mean of its divisors is an integer number (2329956).

Almost surely, 2^21516235 is an apocalyptic number.

21516235 is a deficient number, since it is larger than the sum of its proper divisors (6443237).

21516235 is a wasteful number, since it uses less digits than its factorization.

21516235 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25494 (or 25481 counting only the distinct ones).

The product of its digits is 1800, while the sum is 25.

The square root of 21516235 is about 4638.5595824566. The cubic root of 21516235 is about 278.1348611577.

Adding to 21516235 its reverse (53261512), we get a palindrome (74777747).

The spelling of 21516235 in words is "twenty-one million, five hundred sixteen thousand, two hundred thirty-five".