21251165 has 8 divisors (see below), whose sum is σ = 27463128. Its totient is φ = 15693120.

The previous prime is 21251141. The next prime is 21251179. The reversal of 21251165 is 56115212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4301476 + 16949689 = 2074^2 + 4117^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21251165 - 2¹² = 21247069 is a prime.

It is a super-2 number, since 2×21251165² = 903224027714450, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21251165.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 163406 + ... + 163535.

It is an arithmetic number, because the mean of its divisors is an integer number (3432891).

Almost surely, 2^21251165 is an apocalyptic number.

It is an amenable number.

21251165 is a deficient number, since it is larger than the sum of its proper divisors (6211963).

21251165 is a wasteful number, since it uses less digits than its factorization.

21251165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 326959.

The product of its digits is 600, while the sum is 23.

The square root of 21251165 is about 4609.8985889063. The cubic root of 21251165 is about 276.9879744722.

Adding to 21251165 its reverse (56115212), we get a palindrome (77366377).

The spelling of 21251165 in words is "twenty-one million, two hundred fifty-one thousand, one hundred sixty-five".