21697216 has 28 divisors (see below), whose sum is σ = 43223688. Its totient is φ = 10806272.

The previous prime is 21697201. The next prime is 21697217. The reversal of 21697216 is 61279612.

It is not an unprimeable number, because it can be changed into a prime (21697217) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21720 + ... + 22696.

Almost surely, 2^21697216 is an apocalyptic number.

It is an amenable number.

21697216 is a deficient number, since it is larger than the sum of its proper divisors (21526472).

21697216 is an equidigital number, since it uses as much as digits as its factorization.

21697216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1336 (or 1326 counting only the distinct ones).

The product of its digits is 9072, while the sum is 34.

The square root of 21697216 is about 4658.0270501576. The cubic root of 21697216 is about 278.9125165179.

The spelling of 21697216 in words is "twenty-one million, six hundred ninety-seven thousand, two hundred sixteen".