21991803448365 has 24 divisors (see below), whose sum is σ = 38838354773400. Its totient is φ = 11507660671104.

The previous prime is 21991803448339. The next prime is 21991803448393. The reversal of 21991803448365 is 56384430819912.

21991803448365 is a `hidden beast` number, since 2 + 1 + 9 + 9 + 180 + 3 + 448 + 3 + 6 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1615435916004 + 20376367532361 = 1270998^2 + 4514019^2 .

It is not a de Polignac number, because 21991803448365 - 2¹² = 21991803444269 is a prime.

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 23 ways as a sum of consecutive naturals, for example, 4610438590 + ... + 4610443359.

It is an arithmetic number, because the mean of its divisors is an integer number (1618264782225).

Almost surely, 2^{21991803448365} is an apocalyptic number.

It is an amenable number.

21991803448365 is a deficient number, since it is larger than the sum of its proper divisors (16846551325035).

21991803448365 is a wasteful number, since it uses less digits than its factorization.

21991803448365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9220882013 (or 9220882010 counting only the distinct ones).

The product of its (nonzero) digits is 44789760, while the sum is 63.

The spelling of 21991803448365 in words is "twenty-one trillion, nine hundred ninety-one billion, eight hundred three million, four hundred forty-eight thousand, three hundred sixty-five".