7904921 has 4 divisors (see below), whose sum is σ = 7912500. Its totient is φ = 7897344.

The previous prime is 7904903. The next prime is 7904947. The reversal of 7904921 is 1294097.

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 4682896 + 3222025 = 2164^2 + 1795^2 .

It is a cyclic number.

It is not a de Polignac number, because 7904921 - 2⁶ = 7904857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7904321) 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, 1916 + ... + 4413.

It is an arithmetic number, because the mean of its divisors is an integer number (1978125).

Almost surely, 2^7904921 is an apocalyptic number.

It is an amenable number.

7904921 is a deficient number, since it is larger than the sum of its proper divisors (7579).

7904921 is a wasteful number, since it uses less digits than its factorization.

7904921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7578.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 7904921 is about 2811.5691348427. The cubic root of 7904921 is about 199.2045152146.

The spelling of 7904921 in words is "seven million, nine hundred four thousand, nine hundred twenty-one".