7856421 has 4 divisors (see below), whose sum is σ = 10475232. Its totient is φ = 5237612.

The previous prime is 7856417. The next prime is 7856441. The reversal of 7856421 is 1246587.

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 7856421 - 2² = 7856417 is a prime.

7856421 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7856411) 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, 1309401 + ... + 1309406.

It is an arithmetic number, because the mean of its divisors is an integer number (2618808).

Almost surely, 2^7856421 is an apocalyptic number.

It is an amenable number.

7856421 is a deficient number, since it is larger than the sum of its proper divisors (2618811).

7856421 is a wasteful number, since it uses less digits than its factorization.

7856421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2618810.

The product of its digits is 13440, while the sum is 33.

The square root of 7856421 is about 2802.9307875865. The cubic root of 7856421 is about 198.7962781361.

The spelling of 7856421 in words is "seven million, eight hundred fifty-six thousand, four hundred twenty-one".