21165945089 has 4 divisors (see below), whose sum is σ = 21173224020. Its totient is φ = 21158666160.

The previous prime is 21165945061. The next prime is 21165945103. The reversal of 21165945089 is 98054956112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20077473025 + 1088472064 = 141695^2 + 32992^2 .

It is a cyclic number.

It is not a de Polignac number, because 21165945089 - 2¹² = 21165940993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21165945989) 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, 3635102 + ... + 3640919.

It is an arithmetic number, because the mean of its divisors is an integer number (5293306005).

Almost surely, 2^21165945089 is an apocalyptic number.

It is an amenable number.

21165945089 is a deficient number, since it is larger than the sum of its proper divisors (7278931).

21165945089 is an equidigital number, since it uses as much as digits as its factorization.

21165945089 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7278930.

The product of its (nonzero) digits is 777600, while the sum is 50.

The spelling of 21165945089 in words is "twenty-one billion, one hundred sixty-five million, nine hundred forty-five thousand, eighty-nine".