1661890 has 8 divisors (see below), whose sum is σ = 2991420. Its totient is φ = 664752.

The previous prime is 1661887. The next prime is 1661893. The reversal of 1661890 is 981661.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1661887) and next prime (1661893).

It can be written as a sum of positive squares in 2 ways, for example, as 1610361 + 51529 = 1269^2 + 227^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (1661893) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 83085 + ... + 83104.

2^1661890 is an apocalyptic number.

1661890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1661890 is a deficient number, since it is larger than the sum of its proper divisors (1329530).

1661890 is a wasteful number, since it uses less digits than its factorization.

1661890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166196.

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

The square root of 1661890 is about 1289.1431262664. The cubic root of 1661890 is about 118.4497344778.

The spelling of 1661890 in words is "one million, six hundred sixty-one thousand, eight hundred ninety".