1664673971 has 4 divisors (see below), whose sum is σ = 1665047832. Its totient is φ = 1664300112.

The previous prime is 1664673953. The next prime is 1664674003. The reversal of 1664673971 is 1793764661.

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-1664673971 is a prime.

It is a super-2 number, since 2×1664673971² = 5542278859449817682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664678971) 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, 180170 + ... + 189183.

It is an arithmetic number, because the mean of its divisors is an integer number (416261958).

Almost surely, 2^1664673971 is an apocalyptic number.

1664673971 is a deficient number, since it is larger than the sum of its proper divisors (373861).

1664673971 is an equidigital number, since it uses as much as digits as its factorization.

1664673971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 373860.

The product of its digits is 1143072, while the sum is 50.

The square root of 1664673971 is about 40800.4163091506. The cubic root of 1664673971 is about 1185.1583926620.

The spelling of 1664673971 in words is "one billion, six hundred sixty-four million, six hundred seventy-three thousand, nine hundred seventy-one".