851981 has 4 divisors (see below), whose sum is σ = 917532. Its totient is φ = 786432.

The previous prime is 851971. The next prime is 852011. The reversal of 851981 is 189158.

It is a happy number.

851981 is nontrivially palindromic in base 16.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 586756 + 265225 = 766^2 + 515^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-851981 is a prime.

It is a super-2 number, since 2×851981² = 1451743248722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (851971) 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, 32756 + ... + 32781.

It is an arithmetic number, because the mean of its divisors is an integer number (229383).

2⁸⁵¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

851981 is a deficient number, since it is larger than the sum of its proper divisors (65551).

851981 is a wasteful number, since it uses less digits than its factorization.

851981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65550.

The product of its digits is 2880, while the sum is 32.

The square root of 851981 is about 923.0281685843. The cubic root of 851981 is about 94.8003563637.

The spelling of 851981 in words is "eight hundred fifty-one thousand, nine hundred eighty-one".