66655721619 has 24 divisors (see below), whose sum is σ = 100540196640. Its totient is φ = 42473958912.

The previous prime is 66655721609. The next prime is 66655721633. The reversal of 66655721619 is 91612755666.

It is not a de Polignac number, because 66655721619 - 2⁴ = 66655721603 is a prime.

It is a super-2 number, since 2×66655721619² (a number of 22 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66655721609) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 166947 + ... + 401475.

It is an arithmetic number, because the mean of its divisors is an integer number (4189174860).

Almost surely, 2^66655721619 is an apocalyptic number.

66655721619 is a gapful number since it is divisible by the number (69) formed by its first and last digit.

66655721619 is a deficient number, since it is larger than the sum of its proper divisors (33884475021).

66655721619 is a wasteful number, since it uses less digits than its factorization.

66655721619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 235931 (or 235928 counting only the distinct ones).

The product of its digits is 4082400, while the sum is 54.

The spelling of 66655721619 in words is "sixty-six billion, six hundred fifty-five million, seven hundred twenty-one thousand, six hundred nineteen".