21085157521 has 8 divisors (see below), whose sum is σ = 21156859880. Its totient is φ = 21013509888.

The previous prime is 21085157497. The next prime is 21085157537. The reversal of 21085157521 is 12575158012.

It can be written as a sum of positive squares in 4 ways, for example, as 34339600 + 21050817921 = 5860^2 + 145089^2 .

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 21085157521 - 2¹¹ = 21085155473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21085157021) 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 7 ways as a sum of consecutive naturals, for example, 849475 + ... + 873943.

It is an arithmetic number, because the mean of its divisors is an integer number (2644607485).

Almost surely, 2^21085157521 is an apocalyptic number.

It is an amenable number.

21085157521 is a deficient number, since it is larger than the sum of its proper divisors (71702359).

21085157521 is a wasteful number, since it uses less digits than its factorization.

21085157521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27363.

The product of its (nonzero) digits is 28000, while the sum is 37.

The spelling of 21085157521 in words is "twenty-one billion, eighty-five million, one hundred fifty-seven thousand, five hundred twenty-one".