21216659 has 2 divisors, whose sum is σ = 21216660. Its totient is φ = 21216658.

The previous prime is 21216631. The next prime is 21216707. The reversal of 21216659 is 95661212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21216659 - 2²⁴ = 4439443 is a prime.

It is not a weakly prime, because it can be changed into another prime (21216619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608329 + 10608330.

It is an arithmetic number, because the mean of its divisors is an integer number (10608330).

Almost surely, 2^21216659 is an apocalyptic number.

21216659 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216659 is an equidigital number, since it uses as much as digits as its factorization.

21216659 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 32.

The square root of 21216659 is about 4606.1544698371. The cubic root of 21216659 is about 276.8379760327.

The spelling of 21216659 in words is "twenty-one million, two hundred sixteen thousand, six hundred fifty-nine".