987091561 has 4 divisors (see below), whose sum is σ = 987191892. Its totient is φ = 986991232.

The previous prime is 987091543. The next prime is 987091571. The reversal of 987091561 is 165190789.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 337861161 + 649230400 = 18381^2 + 25480^2 .

It is a cyclic number.

It is not a de Polignac number, because 987091561 - 2²⁹ = 450220649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (987091571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33580 + ... + 55693.

It is an arithmetic number, because the mean of its divisors is an integer number (246797973).

Almost surely, 2^987091561 is an apocalyptic number.

It is an amenable number.

987091561 is a deficient number, since it is larger than the sum of its proper divisors (100331).

987091561 is a wasteful number, since it uses less digits than its factorization.

987091561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100330.

The product of its (nonzero) digits is 136080, while the sum is 46.

The square root of 987091561 is about 31418.0133203868. The cubic root of 987091561 is about 995.6785388749.

The spelling of 987091561 in words is "nine hundred eighty-seven million, ninety-one thousand, five hundred sixty-one".