87715781 has 2 divisors, whose sum is σ = 87715782. Its totient is φ = 87715780.

The previous prime is 87715777. The next prime is 87715783. The reversal of 87715781 is 18751778.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59985025 + 27730756 = 7745^2 + 5266^2 .

It is a cyclic number.

It is not a de Polignac number, because 87715781 - 2² = 87715777 is a prime.

It is a super-2 number, since 2×87715781² = 15388116472879922, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 87715783, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (87715783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43857890 + 43857891.

It is an arithmetic number, because the mean of its divisors is an integer number (43857891).

Almost surely, 2^87715781 is an apocalyptic number.

It is an amenable number.

87715781 is a deficient number, since it is larger than the sum of its proper divisors (1).

87715781 is an equidigital number, since it uses as much as digits as its factorization.

87715781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 109760, while the sum is 44.

The square root of 87715781 is about 9365.6703444014. The cubic root of 87715781 is about 444.3166399859.

The spelling of 87715781 in words is "eighty-seven million, seven hundred fifteen thousand, seven hundred eighty-one".