21210643331797 has 4 divisors (see below), whose sum is σ = 21429309757996. Its totient is φ = 20991976905600.

The previous prime is 21210643331711. The next prime is 21210643331803. The reversal of 21210643331797 is 79713334601212.

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 14961973261041 + 6248670070756 = 3868071^2 + 2499734^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210643331797 - 2¹¹ = 21210643329749 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21210643331797.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210643332797) 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, 109333212954 + ... + 109333213147.

It is an arithmetic number, because the mean of its divisors is an integer number (5357327439499).

Almost surely, 2^{21210643331797} is an apocalyptic number.

It is an amenable number.

21210643331797 is a deficient number, since it is larger than the sum of its proper divisors (218666426199).

21210643331797 is an equidigital number, since it uses as much as digits as its factorization.

21210643331797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218666426198.

The product of its (nonzero) digits is 1143072, while the sum is 49.

The spelling of 21210643331797 in words is "twenty-one trillion, two hundred ten billion, six hundred forty-three million, three hundred thirty-one thousand, seven hundred ninety-seven".