1664491778 has 16 divisors (see below), whose sum is σ = 2514395520. Its totient is φ = 826369776.

The previous prime is 1664491757. The next prime is 1664491783. The reversal of 1664491778 is 8771944661.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 532103 + ... + 535221.

It is an arithmetic number, because the mean of its divisors is an integer number (157149720).

Almost surely, 2^1664491778 is an apocalyptic number.

1664491778 is a deficient number, since it is larger than the sum of its proper divisors (849903742).

1664491778 is a wasteful number, since it uses less digits than its factorization.

1664491778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4921.

The product of its digits is 2032128, while the sum is 53.

The square root of 1664491778 is about 40798.1835134850. The cubic root of 1664491778 is about 1185.1151538767.

It can be divided in two parts, 166 and 4491778, that added together give a palindrome (4491944).

The spelling of 1664491778 in words is "one billion, six hundred sixty-four million, four hundred ninety-one thousand, seven hundred seventy-eight".