1661986 has 8 divisors (see below), whose sum is σ = 2521260. Its totient is φ = 821568.

The previous prime is 1661983. The next prime is 1662007. The reversal of 1661986 is 6891661.

It can be written as a sum of positive squares in 2 ways, for example, as 1640961 + 21025 = 1281^2 + 145^2 .

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 (1661983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4491 + ... + 4846.

2^1661986 is an apocalyptic number.

1661986 is a deficient number, since it is larger than the sum of its proper divisors (859274).

1661986 is an equidigital number, since it uses as much as digits as its factorization.

1661986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9428.

The product of its digits is 15552, while the sum is 37.

The square root of 1661986 is about 1289.1803597635. The cubic root of 1661986 is about 118.4520152055.

The spelling of 1661986 in words is "one million, six hundred sixty-one thousand, nine hundred eighty-six".