1721061720866 has 4 divisors (see below), whose sum is σ = 2581592581302. Its totient is φ = 860530860432.

The previous prime is 1721061720809. The next prime is 1721061720901. The reversal of 1721061720866 is 6680271601271.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 1538629372225 + 182432348641 = 1240415^2 + 427121^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1721061720866.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430265430215 + ... + 430265430218.

Almost surely, 2^{1721061720866} is an apocalyptic number.

1721061720866 is a deficient number, since it is larger than the sum of its proper divisors (860530860436).

1721061720866 is an equidigital number, since it uses as much as digits as its factorization.

1721061720866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860530860435.

The product of its (nonzero) digits is 338688, while the sum is 47.

The spelling of 1721061720866 in words is "one trillion, seven hundred twenty-one billion, sixty-one million, seven hundred twenty thousand, eight hundred sixty-six".