21647216 has 20 divisors (see below), whose sum is σ = 42054600. Its totient is φ = 10794432.

The previous prime is 21647191. The next prime is 21647243. The reversal of 21647216 is 61274612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5090 + ... + 8318.

It is an arithmetic number, because the mean of its divisors is an integer number (2102730).

Almost surely, 2^21647216 is an apocalyptic number.

It is an amenable number.

21647216 is a deficient number, since it is larger than the sum of its proper divisors (20407384).

21647216 is a wasteful number, since it uses less digits than its factorization.

21647216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3656 (or 3650 counting only the distinct ones).

The product of its digits is 4032, while the sum is 29.

The square root of 21647216 is about 4652.6568753778. The cubic root of 21647216 is about 278.6981057249.

The spelling of 21647216 in words is "twenty-one million, six hundred forty-seven thousand, two hundred sixteen".