21353665 has 8 divisors (see below), whose sum is σ = 25795008. Its totient is φ = 16969200.

The previous prime is 21353639. The next prime is 21353711. The reversal of 21353665 is 56635312.

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

It is not a de Polignac number, because 21353665 - 2⁷ = 21353537 is a prime.

It is a Duffinian number.

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 7 ways as a sum of consecutive naturals, for example, 13387 + ... + 14896.

It is an arithmetic number, because the mean of its divisors is an integer number (3224376).

Almost surely, 2^21353665 is an apocalyptic number.

It is an amenable number.

21353665 is a deficient number, since it is larger than the sum of its proper divisors (4441343).

21353665 is a wasteful number, since it uses less digits than its factorization.

21353665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28439.

The product of its digits is 16200, while the sum is 31.

The square root of 21353665 is about 4621.0025968398. The cubic root of 21353665 is about 277.4325892043.

Adding to 21353665 its reverse (56635312), we get a palindrome (77988977).

The spelling of 21353665 in words is "twenty-one million, three hundred fifty-three thousand, six hundred sixty-five".