666021700651 has 4 divisors (see below), whose sum is σ = 666037091232. Its totient is φ = 666006310072.

The previous prime is 666021700633. The next prime is 666021700711. The reversal of 666021700651 is 156007120666.

666021700651 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 156007120666 = 2 ⋅78003560333.

It is a cyclic number.

It is not a de Polignac number, because 666021700651 - 2¹³ = 666021692459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666021700601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7630195 + ... + 7716988.

It is an arithmetic number, because the mean of its divisors is an integer number (166509272808).

Almost surely, 2^666021700651 is an apocalyptic number.

666021700651 is a deficient number, since it is larger than the sum of its proper divisors (15390581).

666021700651 is a wasteful number, since it uses less digits than its factorization.

666021700651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15390580.

The product of its (nonzero) digits is 90720, while the sum is 40.

The spelling of 666021700651 in words is "six hundred sixty-six billion, twenty-one million, seven hundred thousand, six hundred fifty-one".