1649985581 has 2 divisors, whose sum is σ = 1649985582. Its totient is φ = 1649985580.

The previous prime is 1649985529. The next prime is 1649985587. The reversal of 1649985581 is 1855899461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 845355625 + 804629956 = 29075^2 + 28366^2 .

It is a cyclic number.

It is not a de Polignac number, because 1649985581 - 2¹⁴ = 1649969197 is a prime.

It is a super-2 number, since 2×1649985581² = 5444904835015815122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1649985587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 824992790 + 824992791.

It is an arithmetic number, because the mean of its divisors is an integer number (824992791).

Almost surely, 2^1649985581 is an apocalyptic number.

It is an amenable number.

1649985581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1649985581 is an equidigital number, since it uses as much as digits as its factorization.

1649985581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3110400, while the sum is 56.

The square root of 1649985581 is about 40620.0145371712. The cubic root of 1649985581 is about 1181.6623083487.

The spelling of 1649985581 in words is "one billion, six hundred forty-nine million, nine hundred eighty-five thousand, five hundred eighty-one".