261507989 has 4 divisors (see below), whose sum is σ = 266442156. Its totient is φ = 256573824.

The previous prime is 261507979. The next prime is 261508003. The reversal of 261507989 is 989705162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 137007025 + 124500964 = 11705^2 + 11158^2 .

It is a cyclic number.

It is not a de Polignac number, because 261507989 - 2⁸ = 261507733 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 (261507919) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2467004 + ... + 2467109.

It is an arithmetic number, because the mean of its divisors is an integer number (66610539).

Almost surely, 2^261507989 is an apocalyptic number.

It is an amenable number.

261507989 is a deficient number, since it is larger than the sum of its proper divisors (4934167).

261507989 is an equidigital number, since it uses as much as digits as its factorization.

261507989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4934166.

The product of its (nonzero) digits is 272160, while the sum is 47.

The square root of 261507989 is about 16171.2086437594. The cubic root of 261507989 is about 639.4819937700.

The spelling of 261507989 in words is "two hundred sixty-one million, five hundred seven thousand, nine hundred eighty-nine".