7856921 has 2 divisors, whose sum is σ = 7856922. Its totient is φ = 7856920.

The previous prime is 7856911. The next prime is 7856939. The reversal of 7856921 is 1296587.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7778521 + 78400 = 2789^2 + 280^2 .

It is an emirp because it is prime and its reverse (1296587) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7856921 - 2¹⁴ = 7840537 is a prime.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is not a weakly prime, because it can be changed into another prime (7856911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3928460 + 3928461.

It is an arithmetic number, because the mean of its divisors is an integer number (3928461).

Almost surely, 2^7856921 is an apocalyptic number.

It is an amenable number.

7856921 is a deficient number, since it is larger than the sum of its proper divisors (1).

7856921 is an equidigital number, since it uses as much as digits as its factorization.

7856921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 38.

The square root of 7856921 is about 2803.0199785232. The cubic root of 7856921 is about 198.8004953248.

The spelling of 7856921 in words is "seven million, eight hundred fifty-six thousand, nine hundred twenty-one".