66354231721 has 4 divisors (see below), whose sum is σ = 66354768000. Its totient is φ = 66353695444.

The previous prime is 66354231673. The next prime is 66354231799. The reversal of 66354231721 is 12713245366.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12713245366 = 2 ⋅6356622683.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66354231721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66354235721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22380 + ... + 364978.

It is an arithmetic number, because the mean of its divisors is an integer number (16588692000).

Almost surely, 2^66354231721 is an apocalyptic number.

It is an amenable number.

66354231721 is a deficient number, since it is larger than the sum of its proper divisors (536279).

66354231721 is a wasteful number, since it uses less digits than its factorization.

66354231721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 536278.

The product of its digits is 181440, while the sum is 40.

The spelling of 66354231721 in words is "sixty-six billion, three hundred fifty-four million, two hundred thirty-one thousand, seven hundred twenty-one".