7881821 has 4 divisors (see below), whose sum is σ = 7894944. Its totient is φ = 7868700.

The previous prime is 7881817. The next prime is 7881859. The reversal of 7881821 is 1281887.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1281887 = 29 ⋅44203.

It is a cyclic number.

It is not a de Polignac number, because 7881821 - 2² = 7881817 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 (7881221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5615 + ... + 6876.

It is an arithmetic number, because the mean of its divisors is an integer number (1973736).

Almost surely, 2^7881821 is an apocalyptic number.

It is an amenable number.

7881821 is a deficient number, since it is larger than the sum of its proper divisors (13123).

7881821 is a wasteful number, since it uses less digits than its factorization.

7881821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13122.

The product of its digits is 7168, while the sum is 35.

The square root of 7881821 is about 2807.4581029821. The cubic root of 7881821 is about 199.0102854039.

The spelling of 7881821 in words is "seven million, eight hundred eighty-one thousand, eight hundred twenty-one".