21605265755253 has 6 divisors (see below), whose sum is σ = 31207606090934. Its totient is φ = 14403510503496.

The previous prime is 21605265755237. The next prime is 21605265755287. The reversal of 21605265755253 is 35255756250612.

21605265755253 is a `hidden beast` number, since 2 + 1 + 6 + 0 + 52 + 65 + 7 + 5 + 525 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 16612977113604 + 4992288641649 = 4075902^2 + 2234343^2 .

It is not a de Polignac number, because 21605265755253 - 2⁴ = 21605265755237 is a prime.

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 21605265755253.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605265755053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1200292541950 + ... + 1200292541967.

Almost surely, 2^{21605265755253} is an apocalyptic number.

It is an amenable number.

21605265755253 is a deficient number, since it is larger than the sum of its proper divisors (9602340335681).

21605265755253 is a wasteful number, since it uses less digits than its factorization.

21605265755253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2400585083923 (or 2400585083920 counting only the distinct ones).

The product of its (nonzero) digits is 18900000, while the sum is 54.

The spelling of 21605265755253 in words is "twenty-one trillion, six hundred five billion, two hundred sixty-five million, seven hundred fifty-five thousand, two hundred fifty-three".