21403265 has 8 divisors (see below), whose sum is σ = 27659688. Its totient is φ = 15805440.

The previous prime is 21403259. The next prime is 21403273. The reversal of 21403265 is 56230412.

It can be written as a sum of positive squares in 4 ways, for example, as 1117249 + 20286016 = 1057^2 + 4504^2 .

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

It is not a de Polignac number, because 21403265 - 2²⁰ = 20354689 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21403265.

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, 164576 + ... + 164705.

It is an arithmetic number, because the mean of its divisors is an integer number (3457461).

Almost surely, 2^21403265 is an apocalyptic number.

It is an amenable number.

21403265 is a deficient number, since it is larger than the sum of its proper divisors (6256423).

21403265 is a wasteful number, since it uses less digits than its factorization.

21403265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329299.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21403265 is about 4626.3662846774. The cubic root of 21403265 is about 277.6472286397.

Adding to 21403265 its reverse (56230412), we get a palindrome (77633677).

The spelling of 21403265 in words is "twenty-one million, four hundred three thousand, two hundred sixty-five".