21216066 has 16 divisors (see below), whose sum is σ = 42484224. Its totient is φ = 7063344.

The previous prime is 21216061. The next prime is 21216073. The reversal of 21216066 is 66061212.

It is not an unprimeable number, because it can be changed into a prime (21216061) 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, 4896 + ... + 8148.

It is an arithmetic number, because the mean of its divisors is an integer number (2655264).

Almost surely, 2^21216066 is an apocalyptic number.

21216066 is an abundant number, since it is smaller than the sum of its proper divisors (21268158).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21216066 is a wasteful number, since it uses less digits than its factorization.

21216066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4345.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21216066 is about 4606.0900989885. The cubic root of 21216066 is about 276.8353968260.

Adding to 21216066 its reverse (66061212), we get a palindrome (87277278).

It can be divided in two parts, 212160 and 66, that added together give a triangular number (212226 = T₆₅₁).

The spelling of 21216066 in words is "twenty-one million, two hundred sixteen thousand, sixty-six".