1990661 has 2 divisors, whose sum is σ = 1990662. Its totient is φ = 1990660.

The previous prime is 1990657. The next prime is 1990679. The reversal of 1990661 is 1660991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1366561 + 624100 = 1169^2 + 790^2 .

It is a cyclic number.

It is not a de Polignac number, because 1990661 - 2² = 1990657 is a prime.

It is a Chen prime.

1990661 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1990621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995330 + 995331.

It is an arithmetic number, because the mean of its divisors is an integer number (995331).

2^1990661 is an apocalyptic number.

It is an amenable number.

1990661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1990661 is an equidigital number, since it uses as much as digits as its factorization.

1990661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 1990661 is about 1410.9078637530. The cubic root of 1990661 is about 125.7956922437.

The spelling of 1990661 in words is "one million, nine hundred ninety thousand, six hundred sixty-one".