666400501 has 4 divisors (see below), whose sum is σ = 717662092. Its totient is φ = 615138912.

The previous prime is 666400487. The next prime is 666400523. The reversal of 666400501 is 105004666.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 190026225 + 476374276 = 13785^2 + 21826^2 .

It is a cyclic number.

It is not a de Polignac number, because 666400501 - 2²¹ = 664303349 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666400501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666400531) 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 3 ways as a sum of consecutive naturals, for example, 25630776 + ... + 25630801.

It is an arithmetic number, because the mean of its divisors is an integer number (179415523).

Almost surely, 2^666400501 is an apocalyptic number.

It is an amenable number.

666400501 is a deficient number, since it is larger than the sum of its proper divisors (51261591).

666400501 is a wasteful number, since it uses less digits than its factorization.

666400501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51261590.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 666400501 is about 25814.7341841825. The cubic root of 666400501 is about 873.4641906975.

The spelling of 666400501 in words is "six hundred sixty-six million, four hundred thousand, five hundred one".