261981 has 16 divisors (see below), whose sum is σ = 401920. Its totient is φ = 168480.

The previous prime is 261977. The next prime is 261983. The reversal of 261981 is 189162.

261981 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 261981 - 2² = 261977 is a prime.

It is a super-2 number, since 2×261981² = 137268088722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

261981 is strictly pandigital in base 7.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 261981.

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

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 681 + ... + 993.

It is an arithmetic number, because the mean of its divisors is an integer number (25120).

2²⁶¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

261981 is a deficient number, since it is larger than the sum of its proper divisors (139939).

261981 is a wasteful number, since it uses less digits than its factorization.

261981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 353 (or 347 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 261981 is about 511.8407955605. The cubic root of 261981 is about 63.9867322757.

The spelling of 261981 in words is "two hundred sixty-one thousand, nine hundred eighty-one".