1981649 has 2 divisors, whose sum is σ = 1981650. Its totient is φ = 1981648.

The previous prime is 1981631. The next prime is 1981663. The reversal of 1981649 is 9461891.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1113025 + 868624 = 1055^2 + 932^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981649 - 2⁸ = 1981393 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1981619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990824 + 990825.

It is an arithmetic number, because the mean of its divisors is an integer number (990825).

2^1981649 is an apocalyptic number.

It is an amenable number.

1981649 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981649 is an equidigital number, since it uses as much as digits as its factorization.

1981649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 38.

The square root of 1981649 is about 1407.7105526350. The cubic root of 1981649 is about 125.6055735082.

The spelling of 1981649 in words is "one million, nine hundred eighty-one thousand, six hundred forty-nine".