3987721 has 4 divisors (see below), whose sum is σ = 3999892. Its totient is φ = 3975552.

The previous prime is 3987677. The next prime is 3987727. The reversal of 3987721 is 1277893.

3987721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1277893 = 683 ⋅1871.

It can be written as a sum of positive squares in 2 ways, for example, as 2595321 + 1392400 = 1611^2 + 1180^2 .

It is a cyclic number.

It is not a de Polignac number, because 3987721 - 2⁷ = 3987593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3987727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5580 + ... + 6253.

It is an arithmetic number, because the mean of its divisors is an integer number (999973).

Almost surely, 2^3987721 is an apocalyptic number.

It is an amenable number.

3987721 is a deficient number, since it is larger than the sum of its proper divisors (12171).

3987721 is a wasteful number, since it uses less digits than its factorization.

3987721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12170.

The product of its digits is 21168, while the sum is 37.

The square root of 3987721 is about 1996.9278905359. The cubic root of 3987721 is about 158.5775078928.

The spelling of 3987721 in words is "three million, nine hundred eighty-seven thousand, seven hundred twenty-one".