1647643342721 has 4 divisors (see below), whose sum is σ = 1647660075732. Its totient is φ = 1647626609712.

The previous prime is 1647643342669. The next prime is 1647643342733. The reversal of 1647643342721 is 1272433467461.

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 779971585600 + 867671757121 = 883160^2 + 931489^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1647643342721 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 1647643342721.

It is not an unprimeable number, because it can be changed into a prime (1647643342021) 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, 8217926 + ... + 8416031.

It is an arithmetic number, because the mean of its divisors is an integer number (411915018933).

Almost surely, 2^{1647643342721} is an apocalyptic number.

It is an amenable number.

1647643342721 is a deficient number, since it is larger than the sum of its proper divisors (16733011).

1647643342721 is an equidigital number, since it uses as much as digits as its factorization.

1647643342721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16733010.

The product of its digits is 4064256, while the sum is 50.

The spelling of 1647643342721 in words is "one trillion, six hundred forty-seven billion, six hundred forty-three million, three hundred forty-two thousand, seven hundred twenty-one".