21165243 has 8 divisors (see below), whose sum is σ = 30785856. Its totient is φ = 12827400.

The previous prime is 21165241. The next prime is 21165251. The reversal of 21165243 is 34256112.

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

It is not a de Polignac number, because 21165243 - 2¹ = 21165241 is a prime.

It is a super-2 number, since 2×21165243² = 895935022498098, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21165241) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 320653 + ... + 320718.

It is an arithmetic number, because the mean of its divisors is an integer number (3848232).

Almost surely, 2^21165243 is an apocalyptic number.

21165243 is a deficient number, since it is larger than the sum of its proper divisors (9620613).

21165243 is a wasteful number, since it uses less digits than its factorization.

21165243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 641385.

The product of its digits is 1440, while the sum is 24.

The square root of 21165243 is about 4600.5698560070. The cubic root of 21165243 is about 276.6141673905.

The spelling of 21165243 in words is "twenty-one million, one hundred sixty-five thousand, two hundred forty-three".