2101921 has 4 divisors (see below), whose sum is σ = 2122432. Its totient is φ = 2081412.

The previous prime is 2101909. The next prime is 2101961. The reversal of 2101921 is 1291012.

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 a de Polignac number, because none of the positive numbers 2^k-2101921 is a prime.

It is a Duffinian number.

2101921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 2101895 and 2101904.

It is not an unprimeable number, because it can be changed into a prime (2101961) 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, 10101 + ... + 10306.

It is an arithmetic number, because the mean of its divisors is an integer number (530608).

2^2101921 is an apocalyptic number.

It is an amenable number.

2101921 is a deficient number, since it is larger than the sum of its proper divisors (20511).

2101921 is a wasteful number, since it uses less digits than its factorization.

2101921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20510.

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 2101921 is about 1449.8003310801. The cubic root of 2101921 is about 128.0969520996.

Adding to 2101921 its reverse (1291012), we get a palindrome (3392933).

The spelling of 2101921 in words is "two million, one hundred one thousand, nine hundred twenty-one".