666789651 has 20 divisors (see below), whose sum is σ = 1086621624. Its totient is φ = 404114400.

The previous prime is 666789583. The next prime is 666789659. The reversal of 666789651 is 156987666.

It is not a de Polignac number, because 666789651 - 2⁷ = 666789523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (666789659) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 373290 + ... + 375071.

Almost surely, 2^666789651 is an apocalyptic number.

666789651 is a deficient number, since it is larger than the sum of its proper divisors (419831973).

666789651 is a wasteful number, since it uses less digits than its factorization.

666789651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 748384 (or 748375 counting only the distinct ones).

The product of its digits is 3265920, while the sum is 54.

The square root of 666789651 is about 25822.2704462640. The cubic root of 666789651 is about 873.6341797889.

The spelling of 666789651 in words is "six hundred sixty-six million, seven hundred eighty-nine thousand, six hundred fifty-one".