666620761 has 3 divisors (see below), whose sum is σ = 666646581. Its totient is φ = 666594942.

The previous prime is 666620737. The next prime is 666620771. The reversal of 666620761 is 167026666.

The square root of 666620761 is 25819.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 666620761 - 2⁵ = 666620729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666620771) 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 2 ways as a sum of consecutive naturals, for example, 12910 + ... + 38728.

It is an arithmetic number, because the mean of its divisors is an integer number (222215527).

Almost surely, 2^666620761 is an apocalyptic number.

666620761 is the 25819-th square number.

666620761 is the 12910-th centered octagonal number.

It is an amenable number.

666620761 is a deficient number, since it is larger than the sum of its proper divisors (25820).

666620761 is an frugal number, since it uses more digits than its factorization.

666620761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51638 (or 25819 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 40.

The cubic root of 666620761 is about 873.5604131292.

The spelling of 666620761 in words is "six hundred sixty-six million, six hundred twenty thousand, seven hundred sixty-one".