2172021 has 4 divisors (see below), whose sum is σ = 2896032. Its totient is φ = 1448012.

The previous prime is 2172007. The next prime is 2172031. The reversal of 2172021 is 1202712.

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 2172021 - 2⁵ = 2171989 is a prime.

It is a D-number.

2172021 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2172031) 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, 362001 + ... + 362006.

It is an arithmetic number, because the mean of its divisors is an integer number (724008).

2^2172021 is an apocalyptic number.

It is an amenable number.

2172021 is a deficient number, since it is larger than the sum of its proper divisors (724011).

2172021 is an equidigital number, since it uses as much as digits as its factorization.

2172021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 724010.

The product of its (nonzero) digits is 56, while the sum is 15.

The square root of 2172021 is about 1473.7777987200. Note that the first 4 decimals coincide. The cubic root of 2172021 is about 129.5054384701.

Adding to 2172021 its reverse (1202712), we get a palindrome (3374733).

The spelling of 2172021 in words is "two million, one hundred seventy-two thousand, twenty-one".