21125935813 has 4 divisors (see below), whose sum is σ = 21415332268. Its totient is φ = 20836539360.

The previous prime is 21125935793. The next prime is 21125935823. The reversal of 21125935813 is 31853952112.

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 9710722849 + 11415212964 = 98543^2 + 106842^2 .

It is a cyclic number.

It is not a de Polignac number, because 21125935813 - 2¹⁷ = 21125804741 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125935823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144698118 + ... + 144698263.

It is an arithmetic number, because the mean of its divisors is an integer number (5353833067).

Almost surely, 2^21125935813 is an apocalyptic number.

It is an amenable number.

21125935813 is a deficient number, since it is larger than the sum of its proper divisors (289396455).

21125935813 is an equidigital number, since it uses as much as digits as its factorization.

21125935813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289396454.

The product of its digits is 64800, while the sum is 40.

The spelling of 21125935813 in words is "twenty-one billion, one hundred twenty-five million, nine hundred thirty-five thousand, eight hundred thirteen".