87731561 has 2 divisors, whose sum is σ = 87731562. Its totient is φ = 87731560.

The previous prime is 87731557. The next prime is 87731597. The reversal of 87731561 is 16513778.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 83083225 + 4648336 = 9115^2 + 2156^2 .

It is a cyclic number.

It is not a de Polignac number, because 87731561 - 2² = 87731557 is a prime.

It is not a weakly prime, because it can be changed into another prime (87731521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43865780 + 43865781.

It is an arithmetic number, because the mean of its divisors is an integer number (43865781).

Almost surely, 2^87731561 is an apocalyptic number.

It is an amenable number.

87731561 is a deficient number, since it is larger than the sum of its proper divisors (1).

87731561 is an equidigital number, since it uses as much as digits as its factorization.

87731561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 35280, while the sum is 38.

The square root of 87731561 is about 9366.5127448800. The cubic root of 87731561 is about 444.3432824596.

The spelling of 87731561 in words is "eighty-seven million, seven hundred thirty-one thousand, five hundred sixty-one".