87191881 has 4 divisors (see below), whose sum is σ = 99647872. Its totient is φ = 74735892.

The previous prime is 87191843. The next prime is 87191887. The reversal of 87191881 is 18819178.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 87191881 - 2⁹ = 87191369 is a prime.

It is a super-2 number, since 2×87191881² = 15204848224636322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (87191887) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6227985 + ... + 6227998.

It is an arithmetic number, because the mean of its divisors is an integer number (24911968).

Almost surely, 2^87191881 is an apocalyptic number.

It is an amenable number.

87191881 is a deficient number, since it is larger than the sum of its proper divisors (12455991).

87191881 is a wasteful number, since it uses less digits than its factorization.

87191881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12455990.

The product of its digits is 32256, while the sum is 43.

The square root of 87191881 is about 9337.6592891367. The cubic root of 87191881 is about 443.4302830666.

The spelling of 87191881 in words is "eighty-seven million, one hundred ninety-one thousand, eight hundred eighty-one".