21026165 has 4 divisors (see below), whose sum is σ = 25231404. Its totient is φ = 16820928.

The previous prime is 21026149. The next prime is 21026171. The reversal of 21026165 is 56162012.

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 12229009 + 8797156 = 3497^2 + 2966^2 .

It is a cyclic number.

It is not a de Polignac number, because 21026165 - 2⁴ = 21026149 is a prime.

It is a super-2 number, since 2×21026165² = 884199229214450, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21026165.

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, 2102612 + ... + 2102621.

It is an arithmetic number, because the mean of its divisors is an integer number (6307851).

Almost surely, 2^21026165 is an apocalyptic number.

It is an amenable number.

21026165 is a deficient number, since it is larger than the sum of its proper divisors (4205239).

21026165 is an equidigital number, since it uses as much as digits as its factorization.

21026165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4205238.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21026165 is about 4585.4296418111. The cubic root of 21026165 is about 276.0069530209.

Adding to 21026165 its reverse (56162012), we get a palindrome (77188177).

The spelling of 21026165 in words is "twenty-one million, twenty-six thousand, one hundred sixty-five".