1664546778 has 12 divisors (see below), whose sum is σ = 3606518058. Its totient is φ = 554848920.

The previous prime is 1664546773. The next prime is 1664546837. The reversal of 1664546778 is 8776454661.

1664546778 is a `hidden beast` number, since 1 + 66 + 454 + 67 + 78 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1618211529 + 46335249 = 40227^2 + 6807^2 .

It is not an unprimeable number, because it can be changed into a prime (1664546773) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 46237393 + ... + 46237428.

Almost surely, 2^1664546778 is an apocalyptic number.

1664546778 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1664546778 is an abundant number, since it is smaller than the sum of its proper divisors (1941971280).

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

1664546778 is a wasteful number, since it uses less digits than its factorization.

1664546778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92474829 (or 92474826 counting only the distinct ones).

The product of its digits is 6773760, while the sum is 54.

The square root of 1664546778 is about 40798.8575575346. The cubic root of 1664546778 is about 1185.1282070333.

The spelling of 1664546778 in words is "one billion, six hundred sixty-four million, five hundred forty-six thousand, seven hundred seventy-eight".