1721393856361 has 3 divisors (see below), whose sum is σ = 1721395168381. Its totient is φ = 1721392544342.

The previous prime is 1721393856341. The next prime is 1721393856367. The reversal of 1721393856361 is 1636583931271.

The square root of 1721393856361 is 1312019.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 1721393856361 - 2¹⁵ = 1721393823593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1721393856367) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 656010 + ... + 1968028.

Almost surely, 2^{1721393856361} is an apocalyptic number.

1721393856361 is the 1312019-th square number.

1721393856361 is the 656010-th centered octagonal number.

It is an amenable number.

1721393856361 is a deficient number, since it is larger than the sum of its proper divisors (1312020).

1721393856361 is an frugal number, since it uses more digits than its factorization.

1721393856361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2624038 (or 1312019 counting only the distinct ones).

The product of its digits is 4898880, while the sum is 55.

The spelling of 1721393856361 in words is "one trillion, seven hundred twenty-one billion, three hundred ninety-three million, eight hundred fifty-six thousand, three hundred sixty-one".