1665281661 has 8 divisors (see below), whose sum is σ = 2220651264. Its totient is φ = 1110049920.

The previous prime is 1665281647. The next prime is 1665281689. The reversal of 1665281661 is 1661825661.

1665281661 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1665281661 - 2¹⁹ = 1664757373 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665281161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1876 + ... + 57741.

It is an arithmetic number, because the mean of its divisors is an integer number (277581408).

Almost surely, 2^1665281661 is an apocalyptic number.

It is an amenable number.

1665281661 is a deficient number, since it is larger than the sum of its proper divisors (555369603).

1665281661 is an equidigital number, since it uses as much as digits as its factorization.

1665281661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68931.

The product of its digits is 103680, while the sum is 42.

The square root of 1665281661 is about 40807.8627350171. The cubic root of 1665281661 is about 1185.3025893228.

The spelling of 1665281661 in words is "one billion, six hundred sixty-five million, two hundred eighty-one thousand, six hundred sixty-one".