87721173 has 12 divisors (see below), whose sum is σ = 134162028. Its totient is φ = 55040640.

The previous prime is 87721133. The next prime is 87721189. The reversal of 87721173 is 37112778.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 43125489 + 44595684 = 6567^2 + 6678^2 .

It is a de Polignac number, because none of the positive numbers 2^k-87721173 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (87721133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 286518 + ... + 286823.

It is an arithmetic number, because the mean of its divisors is an integer number (11180169).

Almost surely, 2^87721173 is an apocalyptic number.

It is an amenable number.

87721173 is a deficient number, since it is larger than the sum of its proper divisors (46440855).

87721173 is a wasteful number, since it uses less digits than its factorization.

87721173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 573364 (or 573361 counting only the distinct ones).

The product of its digits is 16464, while the sum is 36.

The square root of 87721173 is about 9365.9581997786. The cubic root of 87721173 is about 444.3257440346.

The spelling of 87721173 in words is "eighty-seven million, seven hundred twenty-one thousand, one hundred seventy-three".