871611781 has 2 divisors, whose sum is σ = 871611782. Its totient is φ = 871611780.

The previous prime is 871611773. The next prime is 871611787. The reversal of 871611781 is 187116178.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 795747681 + 75864100 = 28209^2 + 8710^2 .

It is a cyclic number.

It is not a de Polignac number, because 871611781 - 2³ = 871611773 is a prime.

It is a super-2 number, since 2×871611781² = 1519414193555983922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (871611787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 435805890 + 435805891.

It is an arithmetic number, because the mean of its divisors is an integer number (435805891).

Almost surely, 2^871611781 is an apocalyptic number.

It is an amenable number.

871611781 is a deficient number, since it is larger than the sum of its proper divisors (1).

871611781 is an equidigital number, since it uses as much as digits as its factorization.

871611781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18816, while the sum is 40.

The square root of 871611781 is about 29523.0720115641. The cubic root of 871611781 is about 955.2294363902.

The spelling of 871611781 in words is "eight hundred seventy-one million, six hundred eleven thousand, seven hundred eighty-one".