3998921 has 4 divisors (see below), whose sum is σ = 4007952. Its totient is φ = 3989892.

The previous prime is 3998899. The next prime is 3998959. The reversal of 3998921 is 1298993.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1298993 = 31 ⋅41903.

It is a cyclic number.

It is not a de Polignac number, because 3998921 - 2¹⁰ = 3997897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3998971) 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, 3815 + ... + 4748.

It is an arithmetic number, because the mean of its divisors is an integer number (1001988).

Almost surely, 2^3998921 is an apocalyptic number.

It is an amenable number.

3998921 is a deficient number, since it is larger than the sum of its proper divisors (9031).

3998921 is an equidigital number, since it uses as much as digits as its factorization.

3998921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9030.

The product of its digits is 34992, while the sum is 41.

The square root of 3998921 is about 1999.7302318063. The cubic root of 3998921 is about 158.7258305321.

The spelling of 3998921 in words is "three million, nine hundred ninety-eight thousand, nine hundred twenty-one".