2100021 has 16 divisors (see below), whose sum is σ = 3491328. Its totient is φ = 1090800.

The previous prime is 2100011. The next prime is 2100031. The reversal of 2100021 is 1200012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (2100011) and next prime (2100031).

It is not a de Polignac number, because 2100021 - 2⁷ = 2099893 is a prime.

It is a Curzon number.

2100021 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 2099982 and 2100009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2100001) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4315 + ... + 4776.

It is an arithmetic number, because the mean of its divisors is an integer number (218208).

2^2100021 is an apocalyptic number.

2100021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2100021 is a deficient number, since it is larger than the sum of its proper divisors (1391307).

2100021 is a wasteful number, since it uses less digits than its factorization.

2100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9112.

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 2100021 is about 1449.1449202892. The cubic root of 2100021 is about 128.0583433570.

Adding to 2100021 its reverse (1200012), we get a palindrome (3300033).

Subtracting from 2100021 its reverse (1200012), we obtain a palindrome (900009).

The spelling of 2100021 in words is "two million, one hundred thousand, twenty-one".