1664549778 has 16 divisors (see below), whose sum is σ = 3332733120. Its totient is φ = 554244336.

The previous prime is 1664549771. The next prime is 1664549807. The reversal of 1664549778 is 8779454661.

It is not an unprimeable number, because it can be changed into a prime (1664549771) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 145425 + ... + 156452.

It is an arithmetic number, because the mean of its divisors is an integer number (208295820).

Almost surely, 2^1664549778 is an apocalyptic number.

1664549778 is an abundant number, since it is smaller than the sum of its proper divisors (1668183342).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1664549778 is a wasteful number, since it uses less digits than its factorization.

1664549778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 302801.

The product of its digits is 10160640, while the sum is 57.

The square root of 1664549778 is about 40798.8943232534. The cubic root of 1664549778 is about 1185.1289190154.

The spelling of 1664549778 in words is "one billion, six hundred sixty-four million, five hundred forty-nine thousand, seven hundred seventy-eight".