1665978890 has 16 divisors (see below), whose sum is σ = 3026275560. Its totient is φ = 660277440.

The previous prime is 1665978883. The next prime is 1665978901. The reversal of 1665978890 is 988795661.

It can be written as a sum of positive squares in 4 ways, for example, as 1221991849 + 443987041 = 34957^2 + 21071^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 763121 + ... + 765300.

Almost surely, 2^1665978890 is an apocalyptic number.

1665978890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1665978890 is a deficient number, since it is larger than the sum of its proper divisors (1360296670).

1665978890 is a wasteful number, since it uses less digits than its factorization.

1665978890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1528537.

The product of its (nonzero) digits is 6531840, while the sum is 59.

The square root of 1665978890 is about 40816.4046677313. The cubic root of 1665978890 is about 1185.4679891763.

The spelling of 1665978890 in words is "one billion, six hundred sixty-five million, nine hundred seventy-eight thousand, eight hundred ninety".