666525401 has 4 divisors (see below), whose sum is σ = 666586932. Its totient is φ = 666463872.

The previous prime is 666525373. The next prime is 666525421. The reversal of 666525401 is 104525666.

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 can be written as a sum of positive squares in 2 ways, for example, as 360240400 + 306285001 = 18980^2 + 17501^2 .

It is a cyclic number.

It is not a de Polignac number, because 666525401 - 2²⁶ = 599416537 is a prime.

It is a super-2 number, since 2×666525401² = 888512220356421602, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666525421) 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, 9716 + ... + 37781.

It is an arithmetic number, because the mean of its divisors is an integer number (166646733).

Almost surely, 2^666525401 is an apocalyptic number.

It is an amenable number.

666525401 is a deficient number, since it is larger than the sum of its proper divisors (61531).

666525401 is a wasteful number, since it uses less digits than its factorization.

666525401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61530.

The product of its (nonzero) digits is 43200, while the sum is 35.

The square root of 666525401 is about 25817.1532319115. The cubic root of 666525401 is about 873.5187569141.

The spelling of 666525401 in words is "six hundred sixty-six million, five hundred twenty-five thousand, four hundred one".