1661890000 has 50 divisors (see below), whose sum is σ = 4023626090. Its totient is φ = 664752000.

The previous prime is 1661889991. The next prime is 1661890033. The reversal of 1661890000 is 981661.

It is a happy number.

It can be written as a sum of positive squares in 5 ways, for example, as 826217536 + 835672464 = 28744^2 + 28908^2 .

It is a tau number, because it is divible by the number of its divisors (50).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 73095 + ... + 93094.

Almost surely, 2^1661890000 is an apocalyptic number.

1661890000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661890000 is an abundant number, since it is smaller than the sum of its proper divisors (2361736090).

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

1661890000 is an equidigital number, since it uses as much as digits as its factorization.

1661890000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166217 (or 166196 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 1661890000 is about 40766.2850895197. The cubic root of 1661890000 is about 1184.4973447780.

The spelling of 1661890000 in words is "one billion, six hundred sixty-one million, eight hundred ninety thousand".