1781532661 has 12 divisors (see below), whose sum is σ = 1816510212. Its totient is φ = 1747178496.

The previous prime is 1781532607. The next prime is 1781532677. The reversal of 1781532661 is 1662351871.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 712569636 + 1068963025 = 26694^2 + 32695^2 .

It is not a de Polignac number, because 1781532661 - 2²⁵ = 1747978229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781532691) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1048965 + ... + 1050661.

It is an arithmetic number, because the mean of its divisors is an integer number (151375851).

Almost surely, 2^1781532661 is an apocalyptic number.

It is an amenable number.

1781532661 is a deficient number, since it is larger than the sum of its proper divisors (34977551).

1781532661 is an equidigital number, since it uses as much as digits as its factorization.

1781532661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2040 (or 1967 counting only the distinct ones).

The product of its digits is 60480, while the sum is 40.

The square root of 1781532661 is about 42208.2060860208. The cubic root of 1781532661 is about 1212.2660132464.

The spelling of 1781532661 in words is "one billion, seven hundred eighty-one million, five hundred thirty-two thousand, six hundred sixty-one".