2156021 has 4 divisors (see below), whose sum is σ = 2464032. Its totient is φ = 1848012.

The previous prime is 2156017. The next prime is 2156023. The reversal of 2156021 is 1206512.

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 2156021 - 2² = 2156017 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 (2156023) 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, 153995 + ... + 154008.

It is an arithmetic number, because the mean of its divisors is an integer number (616008).

2^2156021 is an apocalyptic number.

It is an amenable number.

2156021 is a deficient number, since it is larger than the sum of its proper divisors (308011).

2156021 is an equidigital number, since it uses as much as digits as its factorization.

2156021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308010.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 2156021 is about 1468.3395383902. The cubic root of 2156021 is about 129.1866576528.

The spelling of 2156021 in words is "two million, one hundred fifty-six thousand, twenty-one".