861981 has 4 divisors (see below), whose sum is σ = 1149312. Its totient is φ = 574652.

The previous prime is 861979. The next prime is 861997. The reversal of 861981 is 189168.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 861981 - 2¹ = 861979 is a prime.

It is a super-2 number, since 2×861981² = 1486022488722, which contains 22 as substring.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143661 + ... + 143666.

It is an arithmetic number, because the mean of its divisors is an integer number (287328).

2⁸⁶¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

861981 is a deficient number, since it is larger than the sum of its proper divisors (287331).

861981 is a wasteful number, since it uses less digits than its factorization.

861981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287330.

The product of its digits is 3456, while the sum is 33.

The square root of 861981 is about 928.4293187960. The cubic root of 861981 is about 95.1698163026.

The spelling of 861981 in words is "eight hundred sixty-one thousand, nine hundred eighty-one".