21681653 has 8 divisors (see below), whose sum is σ = 24809280. Its totient is φ = 18561600.

The previous prime is 21681643. The next prime is 21681659. The reversal of 21681653 is 35618612.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21681653 - 2¹⁰ = 21680629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681659) 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, 7118 + ... + 9696.

It is an arithmetic number, because the mean of its divisors is an integer number (3101160).

Almost surely, 2^21681653 is an apocalyptic number.

It is an amenable number.

21681653 is a deficient number, since it is larger than the sum of its proper divisors (3127627).

21681653 is a wasteful number, since it uses less digits than its factorization.

21681653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3787.

The product of its digits is 8640, while the sum is 32.

The square root of 21681653 is about 4656.3561934199. The cubic root of 21681653 is about 278.8458143544.

The spelling of 21681653 in words is "twenty-one million, six hundred eighty-one thousand, six hundred fifty-three".