4021921 has 4 divisors (see below), whose sum is σ = 4061844. Its totient is φ = 3982000.

The previous prime is 4021907. The next prime is 4021933. The reversal of 4021921 is 1291204.

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 3381921 + 640000 = 1839^2 + 800^2 .

It is a cyclic number.

It is not a de Polignac number, because 4021921 - 2⁵ = 4021889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (4021961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19810 + ... + 20011.

It is an arithmetic number, because the mean of its divisors is an integer number (1015461).

Almost surely, 2^4021921 is an apocalyptic number.

It is an amenable number.

4021921 is a deficient number, since it is larger than the sum of its proper divisors (39923).

4021921 is a wasteful number, since it uses less digits than its factorization.

4021921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39922.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 4021921 is about 2005.4727622184. The cubic root of 4021921 is about 159.0295555727.

The spelling of 4021921 in words is "four million, twenty-one thousand, nine hundred twenty-one".