7820921 has 4 divisors (see below), whose sum is σ = 7920000. Its totient is φ = 7721844.

The previous prime is 7820887. The next prime is 7820927. The reversal of 7820921 is 1290287.

It is a happy number.

7820921 is digitally balanced in base 3, 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 a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7820921 is a prime.

It is a super-2 number, since 2×7820921² = 122333610576482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7820927) 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, 49421 + ... + 49578.

It is an arithmetic number, because the mean of its divisors is an integer number (1980000).

Almost surely, 2^7820921 is an apocalyptic number.

It is an amenable number.

7820921 is a deficient number, since it is larger than the sum of its proper divisors (99079).

7820921 is an equidigital number, since it uses as much as digits as its factorization.

7820921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99078.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 7820921 is about 2796.5909604374. The cubic root of 7820921 is about 198.4963992520.

The spelling of 7820921 in words is "seven million, eight hundred twenty thousand, nine hundred twenty-one".