261666811 has 8 divisors (see below), whose sum is σ = 305151200. Its totient is φ = 224285544.

The previous prime is 261666787. The next prime is 261666833. The reversal of 261666811 is 118666162.

It is not a de Polignac number, because 261666811 - 2²³ = 253278203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261666851) 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, 381096 + ... + 381781.

It is an arithmetic number, because the mean of its divisors is an integer number (38143900).

Almost surely, 2^261666811 is an apocalyptic number.

261666811 is a deficient number, since it is larger than the sum of its proper divisors (43484389).

261666811 is an frugal number, since it uses more digits than its factorization.

261666811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 762898 (or 762884 counting only the distinct ones).

The product of its digits is 20736, while the sum is 37.

The square root of 261666811 is about 16176.1185393777. The cubic root of 261666811 is about 639.6114267248.

The spelling of 261666811 in words is "two hundred sixty-one million, six hundred sixty-six thousand, eight hundred eleven".