7821212666 has 8 divisors (see below), whose sum is σ = 11863637460. Its totient is φ = 3866666848.

The previous prime is 7821212653. The next prime is 7821212683. The reversal of 7821212666 is 6662121287.

It can be written as a sum of positive squares in 2 ways, for example, as 7721312641 + 99900025 = 87871^2 + 9995^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×7821212666² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21969521 + ... + 21969876.

Almost surely, 2^7821212666 is an apocalyptic number.

7821212666 is a deficient number, since it is larger than the sum of its proper divisors (4042424794).

7821212666 is a wasteful number, since it uses less digits than its factorization.

7821212666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43939488.

The product of its digits is 96768, while the sum is 41.

The square root of 7821212666 is about 88437.6201963848. The cubic root of 7821212666 is about 1984.9886673337.

The spelling of 7821212666 in words is "seven billion, eight hundred twenty-one million, two hundred twelve thousand, six hundred sixty-six".