261868989 has 4 divisors (see below), whose sum is σ = 349158656. Its totient is φ = 174579324.

The previous prime is 261868979. The next prime is 261868993. The reversal of 261868989 is 989868162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 261868989 - 2¹⁵ = 261836221 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 (261868909) 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, 43644829 + ... + 43644834.

It is an arithmetic number, because the mean of its divisors is an integer number (87289664).

Almost surely, 2^261868989 is an apocalyptic number.

It is an amenable number.

261868989 is a deficient number, since it is larger than the sum of its proper divisors (87289667).

261868989 is an equidigital number, since it uses as much as digits as its factorization.

261868989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87289666.

The product of its digits is 2985984, while the sum is 57.

The square root of 261868989 is about 16182.3666068965. The cubic root of 261868989 is about 639.7761171664.

The spelling of 261868989 in words is "two hundred sixty-one million, eight hundred sixty-eight thousand, nine hundred eighty-nine".