1671721663 has 4 divisors (see below), whose sum is σ = 1681384968. Its totient is φ = 1662058360.

The previous prime is 1671721609. The next prime is 1671721691. The reversal of 1671721663 is 3661271761.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1671721663 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1671721693) 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, 4831393 + ... + 4831738.

It is an arithmetic number, because the mean of its divisors is an integer number (420346242).

Almost surely, 2^1671721663 is an apocalyptic number.

1671721663 is a deficient number, since it is larger than the sum of its proper divisors (9663305).

1671721663 is an equidigital number, since it uses as much as digits as its factorization.

1671721663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9663304.

The product of its digits is 63504, while the sum is 40.

The square root of 1671721663 is about 40886.6929819471. The cubic root of 1671721663 is about 1186.8285638520.

The spelling of 1671721663 in words is "one billion, six hundred seventy-one million, seven hundred twenty-one thousand, six hundred sixty-three".