1266781661 has 8 divisors (see below), whose sum is σ = 1341950880. Its totient is φ = 1192462128.

The previous prime is 1266781619. The next prime is 1266781679. The reversal of 1266781661 is 1661876621.

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 1266781661 - 2³⁰ = 193039837 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 (1266780661) 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, 209351 + ... + 215316.

It is an arithmetic number, because the mean of its divisors is an integer number (167743860).

Almost surely, 2^1266781661 is an apocalyptic number.

It is an amenable number.

1266781661 is a deficient number, since it is larger than the sum of its proper divisors (75169219).

1266781661 is a wasteful number, since it uses less digits than its factorization.

1266781661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 424843.

The product of its digits is 145152, while the sum is 44.

The square root of 1266781661 is about 35591.8763343547. The cubic root of 1266781661 is about 1082.0165971672.

The spelling of 1266781661 in words is "one billion, two hundred sixty-six million, seven hundred eighty-one thousand, six hundred sixty-one".