87731821 has 4 divisors (see below), whose sum is σ = 91546272. Its totient is φ = 83917372.

The previous prime is 87731771. The next prime is 87731827. The reversal of 87731821 is 12813778.

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 a de Polignac number, because none of the positive numbers 2^k-87731821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (87731827) 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, 1907191 + ... + 1907236.

It is an arithmetic number, because the mean of its divisors is an integer number (22886568).

Almost surely, 2^87731821 is an apocalyptic number.

It is an amenable number.

87731821 is a deficient number, since it is larger than the sum of its proper divisors (3814451).

87731821 is a wasteful number, since it uses less digits than its factorization.

87731821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3814450.

The product of its digits is 18816, while the sum is 37.

The square root of 87731821 is about 9366.5266241014. The cubic root of 87731821 is about 444.3437214090.

The spelling of 87731821 in words is "eighty-seven million, seven hundred thirty-one thousand, eight hundred twenty-one".