21253165 has 8 divisors (see below), whose sum is σ = 26046720. Its totient is φ = 16640592.

The previous prime is 21253121. The next prime is 21253181. The reversal of 21253165 is 56135212.

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

It is a cyclic number.

It is not a de Polignac number, because 21253165 - 2⁹ = 21252653 is a prime.

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, 44985 + ... + 45454.

It is an arithmetic number, because the mean of its divisors is an integer number (3255840).

Almost surely, 2^21253165 is an apocalyptic number.

It is an amenable number.

21253165 is a deficient number, since it is larger than the sum of its proper divisors (4793555).

21253165 is an equidigital number, since it uses as much as digits as its factorization.

21253165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90491.

The product of its digits is 1800, while the sum is 25.

The square root of 21253165 is about 4610.1155083143. The cubic root of 21253165 is about 276.9966635420.

Adding to 21253165 its reverse (56135212), we get a palindrome (77388377).

The spelling of 21253165 in words is "twenty-one million, two hundred fifty-three thousand, one hundred sixty-five".