21516434 has 16 divisors (see below), whose sum is σ = 33727320. Its totient is φ = 10281600.

The previous prime is 21516433. The next prime is 21516437. The reversal of 21516434 is 43461512.

It can be written as a sum of positive squares in 4 ways, for example, as 18966025 + 2550409 = 4355^2 + 1597^2 .

It is a zygodrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (21516433) 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, 4022 + ... + 7694.

Almost surely, 2^21516434 is an apocalyptic number.

21516434 is a deficient number, since it is larger than the sum of its proper divisors (12210886).

21516434 is a wasteful number, since it uses less digits than its factorization.

21516434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3805.

The product of its digits is 2880, while the sum is 26.

The square root of 21516434 is about 4638.5810330315. The cubic root of 21516434 is about 278.1357186291.

Adding to 21516434 its reverse (43461512), we get a palindrome (64977946).

The spelling of 21516434 in words is "twenty-one million, five hundred sixteen thousand, four hundred thirty-four".