20813978827897 has 4 divisors (see below), whose sum is σ = 20814040149876. Its totient is φ = 20813917505920.

The previous prime is 20813978827883. The next prime is 20813978827973. The reversal of 20813978827897 is 79872887931802.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2447131477561 + 18366847350336 = 1564331^2 + 4285656^2 .

It is a cyclic number.

It is not a de Polignac number, because 20813978827897 - 2⁴³ = 12017885805689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20813978827847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30149008 + ... + 30831649.

It is an arithmetic number, because the mean of its divisors is an integer number (5203510037469).

Almost surely, 2^{20813978827897} is an apocalyptic number.

It is an amenable number.

20813978827897 is a deficient number, since it is larger than the sum of its proper divisors (61321979).

20813978827897 is an equidigital number, since it uses as much as digits as its factorization.

20813978827897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61321978.

The product of its (nonzero) digits is 1365590016, while the sum is 79.

The spelling of 20813978827897 in words is "twenty trillion, eight hundred thirteen billion, nine hundred seventy-eight million, eight hundred twenty-seven thousand, eight hundred ninety-seven".