66278617921 has 4 divisors (see below), whose sum is σ = 66436801200. Its totient is φ = 66120434644.

The previous prime is 66278617903. The next prime is 66278617939. The reversal of 66278617921 is 12971687266.

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 an emirpimes, since its reverse is a distinct semiprime: 12971687266 = 2 ⋅6485843633.

It is an interprime number because it is at equal distance from previous prime (66278617903) and next prime (66278617939).

It is a cyclic number.

It is not a de Polignac number, because 66278617921 - 2⁹ = 66278617409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66278617021) 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, 79091011 + ... + 79091848.

It is an arithmetic number, because the mean of its divisors is an integer number (16609200300).

Almost surely, 2^66278617921 is an apocalyptic number.

It is an amenable number.

66278617921 is a deficient number, since it is larger than the sum of its proper divisors (158183279).

66278617921 is a wasteful number, since it uses less digits than its factorization.

66278617921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158183278.

The product of its digits is 3048192, while the sum is 55.

The spelling of 66278617921 in words is "sixty-six billion, two hundred seventy-eight million, six hundred seventeen thousand, nine hundred twenty-one".