1649688581 has 2 divisors, whose sum is σ = 1649688582. Its totient is φ = 1649688580.

The previous prime is 1649688569. The next prime is 1649688611. The reversal of 1649688581 is 1858869461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1264940356 + 384748225 = 35566^2 + 19615^2 .

It is a cyclic number.

It is not a de Polignac number, because 1649688581 - 2¹⁸ = 1649426437 is a prime.

It is a super-2 number, since 2×1649688581² = 5442944828563587122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1649688541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 824844290 + 824844291.

It is an arithmetic number, because the mean of its divisors is an integer number (824844291).

Almost surely, 2^1649688581 is an apocalyptic number.

It is an amenable number.

1649688581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1649688581 is an equidigital number, since it uses as much as digits as its factorization.

1649688581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3317760, while the sum is 56.

The square root of 1649688581 is about 40616.3585393866. The cubic root of 1649688581 is about 1181.5914037361.

The spelling of 1649688581 in words is "one billion, six hundred forty-nine million, six hundred eighty-eight thousand, five hundred eighty-one".