21666533 has 8 divisors (see below), whose sum is σ = 24792960. Its totient is φ = 18547920.

The previous prime is 21666493. The next prime is 21666553. The reversal of 21666533 is 33566612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21666533 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21666533.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6368 + ... + 9158.

It is an arithmetic number, because the mean of its divisors is an integer number (3099120).

Almost surely, 2^21666533 is an apocalyptic number.

It is an amenable number.

21666533 is a deficient number, since it is larger than the sum of its proper divisors (3126427).

21666533 is a wasteful number, since it uses less digits than its factorization.

21666533 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3907.

The product of its digits is 19440, while the sum is 32.

The square root of 21666533 is about 4654.7323231309. The cubic root of 21666533 is about 278.7809802885.

The spelling of 21666533 in words is "twenty-one million, six hundred sixty-six thousand, five hundred thirty-three".