21013165 has 4 divisors (see below), whose sum is σ = 25215804. Its totient is φ = 16810528.

The previous prime is 21013159. The next prime is 21013177. The reversal of 21013165 is 56131012.

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 12981609 + 8031556 = 3603^2 + 2834^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013165 - 2⁹ = 21012653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2101312 + ... + 2101321.

It is an arithmetic number, because the mean of its divisors is an integer number (6303951).

Almost surely, 2^21013165 is an apocalyptic number.

It is an amenable number.

21013165 is a deficient number, since it is larger than the sum of its proper divisors (4202639).

21013165 is an equidigital number, since it uses as much as digits as its factorization.

21013165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4202638.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 21013165 is about 4584.0118891643. The cubic root of 21013165 is about 275.9500583515.

Adding to 21013165 its reverse (56131012), we get a palindrome (77144177).

The spelling of 21013165 in words is "twenty-one million, thirteen thousand, one hundred sixty-five".