7821215 has 4 divisors (see below), whose sum is σ = 9385464. Its totient is φ = 6256968.

The previous prime is 7821211. The next prime is 7821221. The reversal of 7821215 is 5121287.

7821215 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.

It is a cyclic number.

It is not a de Polignac number, because 7821215 - 2² = 7821211 is a prime.

It is a super-2 number, since 2×7821215² = 122342808152450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7821211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 782117 + ... + 782126.

It is an arithmetic number, because the mean of its divisors is an integer number (2346366).

Almost surely, 2^7821215 is an apocalyptic number.

7821215 is a deficient number, since it is larger than the sum of its proper divisors (1564249).

7821215 is a wasteful number, since it uses less digits than its factorization.

7821215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1564248.

The product of its digits is 1120, while the sum is 26.

The square root of 7821215 is about 2796.6435239408. The cubic root of 7821215 is about 198.4988864787.

The spelling of 7821215 in words is "seven million, eight hundred twenty-one thousand, two hundred fifteen".