261589987 has 2 divisors, whose sum is σ = 261589988. Its totient is φ = 261589986.

The previous prime is 261589981. The next prime is 261590009. The reversal of 261589987 is 789985162.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 261589987 - 2¹⁹ = 261065699 is a prime.

It is not a weakly prime, because it can be changed into another prime (261589981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130794993 + 130794994.

It is an arithmetic number, because the mean of its divisors is an integer number (130794994).

Almost surely, 2^261589987 is an apocalyptic number.

261589987 is a deficient number, since it is larger than the sum of its proper divisors (1).

261589987 is an equidigital number, since it uses as much as digits as its factorization.

261589987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2177280, while the sum is 55.

The square root of 261589987 is about 16173.7437533800. The cubic root of 261589987 is about 639.5488250805.

The spelling of 261589987 in words is "two hundred sixty-one million, five hundred eighty-nine thousand, nine hundred eighty-seven".