1664445491 has 2 divisors, whose sum is σ = 1664445492. Its totient is φ = 1664445490.

The previous prime is 1664445457. The next prime is 1664445511. The reversal of 1664445491 is 1945444661.

It is a strong prime.

It is an emirp because it is prime and its reverse (1945444661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1664445491 - 2²⁶ = 1597336627 is a prime.

It is not a weakly prime, because it can be changed into another prime (1664442491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832222745 + 832222746.

It is an arithmetic number, because the mean of its divisors is an integer number (832222746).

Almost surely, 2^1664445491 is an apocalyptic number.

1664445491 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664445491 is an equidigital number, since it uses as much as digits as its factorization.

1664445491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 414720, while the sum is 44.

The square root of 1664445491 is about 40797.6162416384. The cubic root of 1664445491 is about 1185.1041683546.

The spelling of 1664445491 in words is "one billion, six hundred sixty-four million, four hundred forty-five thousand, four hundred ninety-one".