261867989 has 2 divisors, whose sum is σ = 261867990. Its totient is φ = 261867988.

The previous prime is 261867967. The next prime is 261868027. The reversal of 261867989 is 989768162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 205692964 + 56175025 = 14342^2 + 7495^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261867989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261867919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130933994 + 130933995.

It is an arithmetic number, because the mean of its divisors is an integer number (130933995).

Almost surely, 2^261867989 is an apocalyptic number.

It is an amenable number.

261867989 is a deficient number, since it is larger than the sum of its proper divisors (1).

261867989 is an equidigital number, since it uses as much as digits as its factorization.

261867989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2612736, while the sum is 56.

The square root of 261867989 is about 16182.3357090378. The cubic root of 261867989 is about 639.7753027936.

It can be divided in two parts, 2618 and 67989, that added together give a palindrome (70607).

The spelling of 261867989 in words is "two hundred sixty-one million, eight hundred sixty-seven thousand, nine hundred eighty-nine".