21105161023621 has 4 divisors (see below), whose sum is σ = 22346641083852. Its totient is φ = 19863680963392.

The previous prime is 21105161023601. The next prime is 21105161023657. The reversal of 21105161023621 is 12632016150112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11989501807396 + 9115659216225 = 3462586^2 + 3019215^2 .

It is not a de Polignac number, because 21105161023621 - 2⁷ = 21105161023493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105161023601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 620740030090 + ... + 620740030123.

It is an arithmetic number, because the mean of its divisors is an integer number (5586660270963).

Almost surely, 2^{21105161023621} is an apocalyptic number.

It is an amenable number.

21105161023621 is a deficient number, since it is larger than the sum of its proper divisors (1241480060231).

21105161023621 is a wasteful number, since it uses less digits than its factorization.

21105161023621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1241480060230.

The product of its (nonzero) digits is 4320, while the sum is 31.

Adding to 21105161023621 its reverse (12632016150112), we get a palindrome (33737177173733).

The spelling of 21105161023621 in words is "twenty-one trillion, one hundred five billion, one hundred sixty-one million, twenty-three thousand, six hundred twenty-one".