666751720 has 32 divisors (see below), whose sum is σ = 1548587520. Its totient is φ = 258096960.

The previous prime is 666751703. The next prime is 666751721. The reversal of 666751720 is 27157666.

It is a happy number.

It is a super-2 number, since 2×666751720² = 889115712245916800, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (666751721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 267612 + ... + 270091.

It is an arithmetic number, because the mean of its divisors is an integer number (48393360).

Almost surely, 2^666751720 is an apocalyptic number.

It is an amenable number.

666751720 is an abundant number, since it is smaller than the sum of its proper divisors (881835800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666751720 is a wasteful number, since it uses less digits than its factorization.

666751720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537745 (or 537741 counting only the distinct ones).

The product of its (nonzero) digits is 105840, while the sum is 40.

The square root of 666751720 is about 25821.5359729045. The cubic root of 666751720 is about 873.6176136218.

The spelling of 666751720 in words is "six hundred sixty-six million, seven hundred fifty-one thousand, seven hundred twenty".