3985921 has 4 divisors (see below), whose sum is σ = 3990532. Its totient is φ = 3981312.

The previous prime is 3985903. The next prime is 3985951. The reversal of 3985921 is 1295893.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1299600 + 2686321 = 1140^2 + 1639^2 .

It is a 3-Lehmer number, since φ(3985921) divides (3985921-1)³.

It is a cyclic number.

It is not a de Polignac number, because 3985921 - 2⁵ = 3985889 is a prime.

It is an Ulam number.

It is a deceptive number, since it divides R_3985920.

It is a Duffinian number.

3985921 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3985951) 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, 576 + ... + 2881.

It is an arithmetic number, because the mean of its divisors is an integer number (997633).

It is a Poulet number, since it divides 2^3985920-1.

Almost surely, 2^3985921 is an apocalyptic number.

3985921 is the 1153-rd octagonal number.

It is an amenable number.

3985921 is a deficient number, since it is larger than the sum of its proper divisors (4611).

3985921 is a wasteful number, since it uses less digits than its factorization.

3985921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4610.

The product of its digits is 19440, while the sum is 37.

The square root of 3985921 is about 1996.4771473773. The cubic root of 3985921 is about 158.5536444319.

The spelling of 3985921 in words is "three million, nine hundred eighty-five thousand, nine hundred twenty-one".