261731309 has 16 divisors (see below), whose sum is σ = 303464448. Its totient is φ = 221106672.

The previous prime is 261731291. The next prime is 261731321. The reversal of 261731309 is 903137162.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 261731309 - 2¹⁶ = 261665773 is a prime.

It is a super-2 number, since 2×261731309² = 137006556221706962, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261731339) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166244 + ... + 167810.

It is an arithmetic number, because the mean of its divisors is an integer number (18966528).

Almost surely, 2^261731309 is an apocalyptic number.

It is an amenable number.

261731309 is a deficient number, since it is larger than the sum of its proper divisors (41733139).

261731309 is a wasteful number, since it uses less digits than its factorization.

261731309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1904.

The product of its (nonzero) digits is 6804, while the sum is 32.

The square root of 261731309 is about 16178.1120344742. The cubic root of 261731309 is about 639.6639748089.

The spelling of 261731309 in words is "two hundred sixty-one million, seven hundred thirty-one thousand, three hundred nine".