1721708755321 has 3 divisors (see below), whose sum is σ = 1721710067461. Its totient is φ = 1721707443182.

The previous prime is 1721708755313. The next prime is 1721708755337. The reversal of 1721708755321 is 1235578071271.

The square root of 1721708755321 is 1312139.

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 1721708755321 - 2³ = 1721708755313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1721708756321) 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, 656070 + ... + 1968208.

Almost surely, 2^{1721708755321} is an apocalyptic number.

1721708755321 is the 1312139-th square number.

1721708755321 is the 656070-th centered octagonal number.

It is an amenable number.

1721708755321 is a deficient number, since it is larger than the sum of its proper divisors (1312140).

1721708755321 is an frugal number, since it uses more digits than its factorization.

1721708755321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2624278 (or 1312139 counting only the distinct ones).

The product of its (nonzero) digits is 823200, while the sum is 49.

Multiplying 1721708755321 by its sum of digits (49), we get a square (84363729010729 = 9184973²).

The spelling of 1721708755321 in words is "one trillion, seven hundred twenty-one billion, seven hundred eight million, seven hundred fifty-five thousand, three hundred twenty-one".