2155421 has 4 divisors (see below), whose sum is σ = 2171292. Its totient is φ = 2139552.

The previous prime is 2155409. The next prime is 2155423. The reversal of 2155421 is 1245512.

2155421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 688900 + 1466521 = 830^2 + 1211^2 .

It is a cyclic number.

It is not a de Polignac number, because 2155421 - 2¹⁸ = 1893277 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2155393 and 2155402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2155423) 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, 7730 + ... + 8003.

It is an arithmetic number, because the mean of its divisors is an integer number (542823).

2^2155421 is an apocalyptic number.

It is an amenable number.

2155421 is a deficient number, since it is larger than the sum of its proper divisors (15871).

2155421 is a wasteful number, since it uses less digits than its factorization.

2155421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15870.

The product of its digits is 400, while the sum is 20.

The square root of 2155421 is about 1468.1352117567. The cubic root of 2155421 is about 129.1746727377.

Subtracting from 2155421 its reverse (1245512), we obtain a palindrome (909909).

The spelling of 2155421 in words is "two million, one hundred fifty-five thousand, four hundred twenty-one".