1280040661 has 4 divisors (see below), whose sum is σ = 1280328192. Its totient is φ = 1279753132.

The previous prime is 1280040649. The next prime is 1280040703. The reversal of 1280040661 is 1660400821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1280040661 - 2⁹ = 1280040149 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 (1280040961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136981 + ... + 146026.

It is an arithmetic number, because the mean of its divisors is an integer number (320082048).

Almost surely, 2^1280040661 is an apocalyptic number.

It is an amenable number.

1280040661 is a deficient number, since it is larger than the sum of its proper divisors (287531).

1280040661 is an equidigital number, since it uses as much as digits as its factorization.

1280040661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287530.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 1280040661 is about 35777.6558902341. The cubic root of 1280040661 is about 1085.7785434886.

The spelling of 1280040661 in words is "one billion, two hundred eighty million, forty thousand, six hundred sixty-one".