87855721 has 4 divisors (see below), whose sum is σ = 87878032. Its totient is φ = 87833412.

The previous prime is 87855697. The next prime is 87855731. The reversal of 87855721 is 12755878.

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 a cyclic number.

It is not a de Polignac number, because 87855721 - 2⁵ = 87855689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (87855731) 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 3 ways as a sum of consecutive naturals, for example, 3495 + ... + 13708.

It is an arithmetic number, because the mean of its divisors is an integer number (21969508).

Almost surely, 2^87855721 is an apocalyptic number.

It is an amenable number.

87855721 is a deficient number, since it is larger than the sum of its proper divisors (22311).

87855721 is a wasteful number, since it uses less digits than its factorization.

87855721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22310.

The product of its digits is 156800, while the sum is 43.

The square root of 87855721 is about 9373.1382684776. The cubic root of 87855721 is about 444.5527990650.

The spelling of 87855721 in words is "eighty-seven million, eight hundred fifty-five thousand, seven hundred twenty-one".