666951763521 has 4 divisors (see below), whose sum is σ = 889269018032. Its totient is φ = 444634509012.

The previous prime is 666951763519. The next prime is 666951763523. The reversal of 666951763521 is 125367159666.

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.

It is an interprime number because it is at equal distance from previous prime (666951763519) and next prime (666951763523).

It is not a de Polignac number, because 666951763521 - 2¹ = 666951763519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666951763523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111158627251 + ... + 111158627256.

It is an arithmetic number, because the mean of its divisors is an integer number (222317254508).

Almost surely, 2^666951763521 is an apocalyptic number.

It is an amenable number.

666951763521 is a deficient number, since it is larger than the sum of its proper divisors (222317254511).

666951763521 is a wasteful number, since it uses less digits than its factorization.

666951763521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222317254510.

The product of its digits is 12247200, while the sum is 57.

The spelling of 666951763521 in words is "six hundred sixty-six billion, nine hundred fifty-one million, seven hundred sixty-three thousand, five hundred twenty-one".