21085072849 has 3 divisors (see below), whose sum is σ = 21085218057. Its totient is φ = 21084927642.

The previous prime is 21085072819. The next prime is 21085072861. The reversal of 21085072849 is 94827058012.

The square root of 21085072849 is 145207.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 21085072849 - 2¹⁹ = 21084548561 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21085072799 and 21085072808.

It is not an unprimeable number, because it can be changed into a prime (21085072819) 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 2 ways as a sum of consecutive naturals, for example, 72604 + ... + 217810.

It is an arithmetic number, because the mean of its divisors is an integer number (7028406019).

Almost surely, 2^21085072849 is an apocalyptic number.

21085072849 is the 145207-th square number.

21085072849 is the 72604-th centered octagonal number.

It is an amenable number.

21085072849 is a deficient number, since it is larger than the sum of its proper divisors (145208).

21085072849 is an frugal number, since it uses more digits than its factorization.

21085072849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290414 (or 145207 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 46.

The spelling of 21085072849 in words is "twenty-one billion, eighty-five million, seventy-two thousand, eight hundred forty-nine".