261988 has 6 divisors (see below), whose sum is σ = 458486. Its totient is φ = 130992.

The previous prime is 261983. The next prime is 262007. The reversal of 261988 is 889162.

It can be written as a sum of positive squares in only one way, i.e., 222784 + 39204 = 472^2 + 198^2 .

It is a nialpdrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (261983) by changing a digit.

261988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32745 + ... + 32752.

2²⁶¹⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

261988 is a deficient number, since it is larger than the sum of its proper divisors (196498).

261988 is a wasteful number, since it uses less digits than its factorization.

261988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65501 (or 65499 counting only the distinct ones).

The product of its digits is 6912, while the sum is 34.

The square root of 261988 is about 511.8476335786. The cubic root of 261988 is about 63.9873021684.

The spelling of 261988 in words is "two hundred sixty-one thousand, nine hundred eighty-eight".