7121636666 has 4 divisors (see below), whose sum is σ = 10682455002. Its totient is φ = 3560818332.

The previous prime is 7121636663. The next prime is 7121636699. The reversal of 7121636666 is 6666361217.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6666361217 = 3761 ⋅1772497.

It can be written as a sum of positive squares in only one way, i.e., 6968743441 + 152893225 = 83479^2 + 12365^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (7121636663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1780409165 + ... + 1780409168.

Almost surely, 2^7121636666 is an apocalyptic number.

7121636666 is a deficient number, since it is larger than the sum of its proper divisors (3560818336).

7121636666 is a wasteful number, since it uses less digits than its factorization.

7121636666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3560818335.

The product of its digits is 326592, while the sum is 44.

The square root of 7121636666 is about 84389.7900578026. The cubic root of 7121636666 is about 1923.9477391605.

The spelling of 7121636666 in words is "seven billion, one hundred twenty-one million, six hundred thirty-six thousand, six hundred sixty-six".