1280161661 has 4 divisors (see below), whose sum is σ = 1288753500. Its totient is φ = 1271569824.

The previous prime is 1280161657. The next prime is 1280161681. The reversal of 1280161661 is 1661610821.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 480968761 + 799192900 = 21931^2 + 28270^2 .

It is a cyclic number.

It is not a de Polignac number, because 1280161661 - 2² = 1280161657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1280161621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4295696 + ... + 4295993.

It is an arithmetic number, because the mean of its divisors is an integer number (322188375).

Almost surely, 2^1280161661 is an apocalyptic number.

It is an amenable number.

1280161661 is a deficient number, since it is larger than the sum of its proper divisors (8591839).

1280161661 is an equidigital number, since it uses as much as digits as its factorization.

1280161661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8591838.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 1280161661 is about 35779.3468498239. The cubic root of 1280161661 is about 1085.8127546582.

The spelling of 1280161661 in words is "one billion, two hundred eighty million, one hundred sixty-one thousand, six hundred sixty-one".