21255535166621 has 4 divisors (see below), whose sum is σ = 24292040190432. Its totient is φ = 18219030142812.

The previous prime is 21255535166573. The next prime is 21255535166623. The reversal of 21255535166621 is 12666153555212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21255535166621 - 2¹⁴ = 21255535150237 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21255535166621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255535166623) 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 3 ways as a sum of consecutive naturals, for example, 1518252511895 + ... + 1518252511908.

It is an arithmetic number, because the mean of its divisors is an integer number (6073010047608).

Almost surely, 2^{21255535166621} is an apocalyptic number.

It is an amenable number.

21255535166621 is a deficient number, since it is larger than the sum of its proper divisors (3036505023811).

21255535166621 is an equidigital number, since it uses as much as digits as its factorization.

21255535166621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3036505023810.

The product of its digits is 3240000, while the sum is 50.

The spelling of 21255535166621 in words is "twenty-one trillion, two hundred fifty-five billion, five hundred thirty-five million, one hundred sixty-six thousand, six hundred twenty-one".