21965689 has 4 divisors (see below), whose sum is σ = 21975156. Its totient is φ = 21956224.

The previous prime is 21965681. The next prime is 21965693. The reversal of 21965689 is 98656912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 12250000 + 9715689 = 3500^2 + 3117^2 .

It is a cyclic number.

It is not a de Polignac number, because 21965689 - 2³ = 21965681 is a prime.

It is a super-3 number, since 3×21965689³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21965681) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1377 + ... + 6769.

It is an arithmetic number, because the mean of its divisors is an integer number (5493789).

Almost surely, 2^21965689 is an apocalyptic number.

It is an amenable number.

21965689 is a deficient number, since it is larger than the sum of its proper divisors (9467).

21965689 is an equidigital number, since it uses as much as digits as its factorization.

21965689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9466.

The product of its digits is 233280, while the sum is 46.

The square root of 21965689 is about 4686.7567677446. The cubic root of 21965689 is about 280.0581894369.

It can be divided in two parts, 2 and 1965689, that added together give a palindrome (1965691).

The spelling of 21965689 in words is "twenty-one million, nine hundred sixty-five thousand, six hundred eighty-nine".