665580401 has 4 divisors (see below), whose sum is σ = 666401904. Its totient is φ = 664758900.

The previous prime is 665580397. The next prime is 665580407. The reversal of 665580401 is 104085566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665580401 - 2² = 665580397 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665580407) 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, 409535 + ... + 411156.

It is an arithmetic number, because the mean of its divisors is an integer number (166600476).

Almost surely, 2^665580401 is an apocalyptic number.

It is an amenable number.

665580401 is a deficient number, since it is larger than the sum of its proper divisors (821503).

665580401 is an equidigital number, since it uses as much as digits as its factorization.

665580401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 821502.

The product of its (nonzero) digits is 28800, while the sum is 35.

The square root of 665580401 is about 25798.8449547649. The cubic root of 665580401 is about 873.1057365695.

The spelling of 665580401 in words is "six hundred sixty-five million, five hundred eighty thousand, four hundred one".