21640213645361 has 4 divisors (see below), whose sum is σ = 22048519563252. Its totient is φ = 21231907727472.

The previous prime is 21640213645333. The next prime is 21640213645417. The reversal of 21640213645361 is 16354631204612.

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 17835544936225 + 3804668709136 = 4223215^2 + 1950556^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21640213645361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21640213645261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 204152958866 + ... + 204152958971.

It is an arithmetic number, because the mean of its divisors is an integer number (5512129890813).

Almost surely, 2^{21640213645361} is an apocalyptic number.

It is an amenable number.

21640213645361 is a deficient number, since it is larger than the sum of its proper divisors (408305917891).

21640213645361 is an equidigital number, since it uses as much as digits as its factorization.

21640213645361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 408305917890.

The product of its (nonzero) digits is 622080, while the sum is 44.

Adding to 21640213645361 its reverse (16354631204612), we get a palindrome (37994844849973).

The spelling of 21640213645361 in words is "twenty-one trillion, six hundred forty billion, two hundred thirteen million, six hundred forty-five thousand, three hundred sixty-one".