21353666 has 8 divisors (see below), whose sum is σ = 33914700. Its totient is φ = 10048768.

The previous prime is 21353639. The next prime is 21353711. The reversal of 21353666 is 66635312.

It can be written as a sum of positive squares in 2 ways, for example, as 21353641 + 25 = 4621^2 + 5^2 .

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

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 313991 + ... + 314058.

Almost surely, 2^21353666 is an apocalyptic number.

21353666 is a deficient number, since it is larger than the sum of its proper divisors (12561034).

21353666 is a wasteful number, since it uses less digits than its factorization.

21353666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 628068.

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

The square root of 21353666 is about 4621.0027050414. The cubic root of 21353666 is about 277.4325935351.

Adding to 21353666 its reverse (66635312), we get a palindrome (87988978).

The spelling of 21353666 in words is "twenty-one million, three hundred fifty-three thousand, six hundred sixty-six".