21634216 has 8 divisors (see below), whose sum is σ = 40564170. Its totient is φ = 10817104.

The previous prime is 21634213. The next prime is 21634253. The reversal of 21634216 is 61243612.

It can be written as a sum of positive squares in only one way, i.e., 12574116 + 9060100 = 3546^2 + 3010^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21634213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1352131 + ... + 1352146.

Almost surely, 2^21634216 is an apocalyptic number.

It is an amenable number.

21634216 is a deficient number, since it is larger than the sum of its proper divisors (18929954).

21634216 is a wasteful number, since it uses less digits than its factorization.

21634216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2704283 (or 2704279 counting only the distinct ones).

The product of its digits is 1728, while the sum is 25.

The square root of 21634216 is about 4651.2596143410. The cubic root of 21634216 is about 278.6423048484.

Adding to 21634216 its reverse (61243612), we get a palindrome (82877828).

The spelling of 21634216 in words is "twenty-one million, six hundred thirty-four thousand, two hundred sixteen".