7821666 has 24 divisors (see below), whose sum is σ = 17944524. Its totient is φ = 2453760.

The previous prime is 7821661. The next prime is 7821691. The reversal of 7821666 is 6661287.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7049025 + 772641 = 2655^2 + 879^2 .

It is a super-2 number, since 2×7821666² = 122356918031112, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 7821666.

It is not an unprimeable number, because it can be changed into a prime (7821661) 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 11 ways as a sum of consecutive naturals, for example, 12475 + ... + 13086.

Almost surely, 2^7821666 is an apocalyptic number.

7821666 is an abundant number, since it is smaller than the sum of its proper divisors (10122858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

7821666 is a wasteful number, since it uses less digits than its factorization.

7821666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25586 (or 25583 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 7821666 is about 2796.7241551501. The cubic root of 7821666 is about 198.5027017971.

The spelling of 7821666 in words is "seven million, eight hundred twenty-one thousand, six hundred sixty-six".