1661345647 has 8 divisors (see below), whose sum is σ = 1791005216. Its totient is φ = 1531952352.

The previous prime is 1661345641. The next prime is 1661345671. The reversal of 1661345647 is 7465431661.

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

It is a cyclic number.

It is not a de Polignac number, because 1661345647 - 2¹⁹ = 1660821359 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661345641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53508 + ... + 78649.

It is an arithmetic number, because the mean of its divisors is an integer number (223875652).

Almost surely, 2^1661345647 is an apocalyptic number.

1661345647 is a deficient number, since it is larger than the sum of its proper divisors (129659569).

1661345647 is a wasteful number, since it uses less digits than its factorization.

1661345647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133137.

The product of its digits is 362880, while the sum is 43.

The square root of 1661345647 is about 40759.6080329534. The cubic root of 1661345647 is about 1184.3680030655.

The spelling of 1661345647 in words is "one billion, six hundred sixty-one million, three hundred forty-five thousand, six hundred forty-seven".