21216669 has 8 divisors (see below), whose sum is σ = 28325472. Its totient is φ = 14126160.

The previous prime is 21216659. The next prime is 21216707. The reversal of 21216669 is 96661212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21216669 - 2⁸ = 21216413 is a prime.

It is a super-2 number, since 2×21216669² = 900294086911122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216619) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1587 + ... + 6704.

It is an arithmetic number, because the mean of its divisors is an integer number (3540684).

Almost surely, 2^21216669 is an apocalyptic number.

It is an amenable number.

21216669 is a deficient number, since it is larger than the sum of its proper divisors (7108803).

21216669 is an equidigital number, since it uses as much as digits as its factorization.

21216669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9147.

The product of its digits is 7776, while the sum is 33.

The square root of 21216669 is about 4606.1555553411. The cubic root of 21216669 is about 276.8380195265.

The spelling of 21216669 in words is "twenty-one million, two hundred sixteen thousand, six hundred sixty-nine".