261690 has 64 divisors (see below), whose sum is σ = 749952. Its totient is φ = 57600.

The previous prime is 261673. The next prime is 261697. The reversal of 261690 is 96162.

It is a super-2 number, since 2×261690² = 136963312200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 261690.

It is not an unprimeable number, because it can be changed into a prime (261697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4260 + ... + 4320.

It is an arithmetic number, because the mean of its divisors is an integer number (11718).

2²⁶¹⁶⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (374976).

261690 is an abundant number, since it is smaller than the sum of its proper divisors (488262).

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

261690 is a wasteful number, since it uses less digits than its factorization.

261690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 261690 is about 511.5564484981. The cubic root of 261690 is about 63.9630320359.

The spelling of 261690 in words is "two hundred sixty-one thousand, six hundred ninety".