21916647 has 6 divisors (see below), whose sum is σ = 31657392. Its totient is φ = 14611092.

The previous prime is 21916607. The next prime is 21916651. The reversal of 21916647 is 74661912.

21916647 is a `hidden beast` number, since 2 + 1 + 9 + 1 + 6 + 647 = 666.

It is not a de Polignac number, because 21916647 - 2¹⁹ = 21392359 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21916607) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1217583 + ... + 1217600.

It is an arithmetic number, because the mean of its divisors is an integer number (5276232).

Almost surely, 2^21916647 is an apocalyptic number.

21916647 is a deficient number, since it is larger than the sum of its proper divisors (9740745).

21916647 is a wasteful number, since it uses less digits than its factorization.

21916647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2435189 (or 2435186 counting only the distinct ones).

The product of its digits is 18144, while the sum is 36.

The square root of 21916647 is about 4681.5218679400. The cubic root of 21916647 is about 279.8496088635.

The spelling of 21916647 in words is "twenty-one million, nine hundred sixteen thousand, six hundred forty-seven".