1664581671 has 10 divisors (see below), whose sum is σ = 2486597432. Its totient is φ = 1109721060.

The previous prime is 1664581669. The next prime is 1664581739. The reversal of 1664581671 is 1761854661.

1664581671 is a `hidden beast` number, since 1 + 6 + 6 + 4 + 581 + 67 + 1 = 666.

It is not a de Polignac number, because 1664581671 - 2¹ = 1664581669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664581601) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 10275115 + ... + 10275276.

Almost surely, 2^1664581671 is an apocalyptic number.

1664581671 is a deficient number, since it is larger than the sum of its proper divisors (822015761).

1664581671 is an equidigital number, since it uses as much as digits as its factorization.

1664581671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20550403 (or 20550394 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 1664581671 is about 40799.2851775616. The cubic root of 1664581671 is about 1185.1364880442.

The spelling of 1664581671 in words is "one billion, six hundred sixty-four million, five hundred eighty-one thousand, six hundred seventy-one".