21243521245 has 8 divisors (see below), whose sum is σ = 25495635384. Its totient is φ = 16992543744.

The previous prime is 21243521209. The next prime is 21243521261. The reversal of 21243521245 is 54212534212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2658742969 + 18584778276 = 51563^2 + 136326^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21243521245 - 2²⁷ = 21109303517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 242484 + ... + 318253.

It is an arithmetic number, because the mean of its divisors is an integer number (3186954423).

Almost surely, 2^21243521245 is an apocalyptic number.

It is an amenable number.

21243521245 is a deficient number, since it is larger than the sum of its proper divisors (4252114139).

21243521245 is an equidigital number, since it uses as much as digits as its factorization.

21243521245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 568319.

The product of its digits is 19200, while the sum is 31.

The spelling of 21243521245 in words is "twenty-one billion, two hundred forty-three million, five hundred twenty-one thousand, two hundred forty-five".