21665735 has 32 divisors (see below), whose sum is σ = 33892992. Its totient is φ = 12902400.

The previous prime is 21665729. The next prime is 21665737. The reversal of 21665735 is 53756612.

It is not a de Polignac number, because 21665735 - 2¹² = 21661639 is a prime.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a junction number, because it is equal to n+sod(n) for n = 21665695 and 21665704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665737) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6335 + ... + 9135.

It is an arithmetic number, because the mean of its divisors is an integer number (1059156).

Almost surely, 2^21665735 is an apocalyptic number.

21665735 is a deficient number, since it is larger than the sum of its proper divisors (12227257).

21665735 is a wasteful number, since it uses less digits than its factorization.

21665735 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2843.

The product of its digits is 37800, while the sum is 35.

The square root of 21665735 is about 4654.6466031268. The cubic root of 21665735 is about 278.7775576528. Note that the first 3 decimals are identical.

The spelling of 21665735 in words is "twenty-one million, six hundred sixty-five thousand, seven hundred thirty-five".