2158421 has 4 divisors (see below), whose sum is σ = 2163072. Its totient is φ = 2153772.

The previous prime is 2158393. The next prime is 2158423. The reversal of 2158421 is 1248512.

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 2158421 - 2⁶ = 2158357 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 (2158423) 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, 1541 + ... + 2586.

It is an arithmetic number, because the mean of its divisors is an integer number (540768).

2^2158421 is an apocalyptic number.

It is an amenable number.

2158421 is a deficient number, since it is larger than the sum of its proper divisors (4651).

2158421 is an equidigital number, since it uses as much as digits as its factorization.

2158421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4650.

The product of its digits is 640, while the sum is 23.

The square root of 2158421 is about 1469.1565607518. The cubic root of 2158421 is about 129.2345750903.

Subtracting from 2158421 its reverse (1248512), we obtain a palindrome (909909).

The spelling of 2158421 in words is "two million, one hundred fifty-eight thousand, four hundred twenty-one".