18021978363997 has 4 divisors (see below), whose sum is σ = 18643425893820. Its totient is φ = 17400530834176.

The previous prime is 18021978363973. The next prime is 18021978364009. The reversal of 18021978363997 is 79936387912081.

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 9529451694361 + 8492526669636 = 3086981^2 + 2914194^2 .

It is a cyclic number.

It is not a de Polignac number, because 18021978363997 - 2¹¹ = 18021978361949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18021978363947) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 310723764868 + ... + 310723764925.

It is an arithmetic number, because the mean of its divisors is an integer number (4660856473455).

Almost surely, 2^{18021978363997} is an apocalyptic number.

It is an amenable number.

18021978363997 is a deficient number, since it is larger than the sum of its proper divisors (621447529823).

18021978363997 is an equidigital number, since it uses as much as digits as its factorization.

18021978363997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 621447529822.

The product of its (nonzero) digits is 246903552, while the sum is 73.

The spelling of 18021978363997 in words is "eighteen trillion, twenty-one billion, nine hundred seventy-eight million, three hundred sixty-three thousand, nine hundred ninety-seven".