21157716245 has 8 divisors (see below), whose sum is σ = 25574583384. Its totient is φ = 16802623744.

The previous prime is 21157716241. The next prime is 21157716277. The reversal of 21157716245 is 54261775112.

It can be written as a sum of positive squares in 4 ways, for example, as 6486208369 + 14671507876 = 80537^2 + 121126^2 .

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 21157716245 - 2² = 21157716241 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157716241) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15442904 + ... + 15444273.

It is an arithmetic number, because the mean of its divisors is an integer number (3196822923).

Almost surely, 2^21157716245 is an apocalyptic number.

It is an amenable number.

21157716245 is a deficient number, since it is larger than the sum of its proper divisors (4416867139).

21157716245 is a wasteful number, since it uses less digits than its factorization.

21157716245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30887319.

The product of its digits is 117600, while the sum is 41.

The spelling of 21157716245 in words is "twenty-one billion, one hundred fifty-seven million, seven hundred sixteen thousand, two hundred forty-five".