21815969 has 8 divisors (see below), whose sum is σ = 25233600. Its totient is φ = 18473616.

The previous prime is 21815939. The next prime is 21815987. The reversal of 21815969 is 96951812.

It is a happy number.

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

It is not a de Polignac number, because 21815969 - 2¹² = 21811873 is a prime.

It is a super-2 number, since 2×21815969² = 951873006817922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21815939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18194 + ... + 19355.

It is an arithmetic number, because the mean of its divisors is an integer number (3154200).

Almost surely, 2^21815969 is an apocalyptic number.

It is an amenable number.

21815969 is a deficient number, since it is larger than the sum of its proper divisors (3417631).

21815969 is an equidigital number, since it uses as much as digits as its factorization.

21815969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37639.

The product of its digits is 38880, while the sum is 41.

The square root of 21815969 is about 4670.7567909280. The cubic root of 21815969 is about 279.4204381182.

The spelling of 21815969 in words is "twenty-one million, eight hundred fifteen thousand, nine hundred sixty-nine".