7905721 has 4 divisors (see below), whose sum is σ = 8249472. Its totient is φ = 7561972.

The previous prime is 7905707. The next prime is 7905727. The reversal of 7905721 is 1275097.

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: 1275097 = 23 ⋅55439.

It is a cyclic number.

It is not a de Polignac number, because 7905721 - 2¹⁹ = 7381433 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7905727) 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, 171841 + ... + 171886.

It is an arithmetic number, because the mean of its divisors is an integer number (2062368).

Almost surely, 2^7905721 is an apocalyptic number.

It is an amenable number.

7905721 is a deficient number, since it is larger than the sum of its proper divisors (343751).

7905721 is a wasteful number, since it uses less digits than its factorization.

7905721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 343750.

The product of its (nonzero) digits is 4410, while the sum is 31.

The square root of 7905721 is about 2811.7114005531. The cubic root of 7905721 is about 199.2112350050.

The spelling of 7905721 in words is "seven million, nine hundred five thousand, seven hundred twenty-one".