7128421 has 4 divisors (see below), whose sum is σ = 7149312. Its totient is φ = 7107532.

The previous prime is 7128391. The next prime is 7128427. The reversal of 7128421 is 1248217.

It is a happy number.

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 7128421 - 2⁷ = 7128293 is a prime.

It is an Ulam number.

It is a Duffinian number.

7128421 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7128427) 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, 9925 + ... + 10618.

It is an arithmetic number, because the mean of its divisors is an integer number (1787328).

Almost surely, 2^7128421 is an apocalyptic number.

It is an amenable number.

7128421 is a deficient number, since it is larger than the sum of its proper divisors (20891).

7128421 is a wasteful number, since it uses less digits than its factorization.

7128421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20890.

The product of its digits is 896, while the sum is 25.

The square root of 7128421 is about 2669.9102981186. The cubic root of 7128421 is about 192.4558486476.

The spelling of 7128421 in words is "seven million, one hundred twenty-eight thousand, four hundred twenty-one".