189781 has 4 divisors (see below), whose sum is σ = 191052. Its totient is φ = 188512.

The previous prime is 189767. The next prime is 189797. The reversal of 189781 is 187981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 187981 = 317 ⋅593.

It can be written as a sum of positive squares in 2 ways, for example, as 119025 + 70756 = 345^2 + 266^2 .

It is a cyclic number.

It is not a de Polignac number, because 189781 - 2⁷ = 189653 is a prime.

It is a super-2 number, since 2×189781² = 72033655922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (189701) 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, 376 + ... + 721.

It is an arithmetic number, because the mean of its divisors is an integer number (47763).

2¹⁸⁹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

189781 is a deficient number, since it is larger than the sum of its proper divisors (1271).

189781 is a wasteful number, since it uses less digits than its factorization.

189781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1270.

The product of its digits is 4032, while the sum is 34.

The square root of 189781 is about 435.6386116955. The cubic root of 189781 is about 57.4668744299.

The spelling of 189781 in words is "one hundred eighty-nine thousand, seven hundred eighty-one".