1205266661 has 4 divisors (see below), whose sum is σ = 1207214400. Its totient is φ = 1203318924.

The previous prime is 1205266649. The next prime is 1205266717. The reversal of 1205266661 is 1666625021.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1666625021 = 10223 ⋅163027.

It is a cyclic number.

It is not a de Polignac number, because 1205266661 - 2¹⁰ = 1205265637 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 (1205266061) 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, 972941 + ... + 974178.

It is an arithmetic number, because the mean of its divisors is an integer number (301803600).

Almost surely, 2^1205266661 is an apocalyptic number.

It is an amenable number.

1205266661 is a deficient number, since it is larger than the sum of its proper divisors (1947739).

1205266661 is an equidigital number, since it uses as much as digits as its factorization.

1205266661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1947738.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 1205266661 is about 34716.9506293396. The cubic root of 1205266661 is about 1064.2109288068.

The spelling of 1205266661 in words is "one billion, two hundred five million, two hundred sixty-six thousand, six hundred sixty-one".