261211566 has 32 divisors (see below), whose sum is σ = 651333888. Its totient is φ = 67847040.

The previous prime is 261211543. The next prime is 261211589. The reversal of 261211566 is 665112162.

261211566 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (261211543) and next prime (261211589).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 282235 + ... + 283158.

It is an arithmetic number, because the mean of its divisors is an integer number (20354184).

Almost surely, 2^261211566 is an apocalyptic number.

261211566 is an abundant number, since it is smaller than the sum of its proper divisors (390122322).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261211566 is a wasteful number, since it uses less digits than its factorization.

261211566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 565416.

The product of its digits is 4320, while the sum is 30.

The square root of 261211566 is about 16162.0408983519. The cubic root of 261211566 is about 639.2402817942.

The spelling of 261211566 in words is "two hundred sixty-one million, two hundred eleven thousand, five hundred sixty-six".