665800421 has 32 divisors (see below), whose sum is σ = 802615296. Its totient is φ = 544320000.

The previous prime is 665800411. The next prime is 665800439. The reversal of 665800421 is 124008566.

It is a cyclic number.

It is not a de Polignac number, because 665800421 - 2²⁶ = 598691557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665800411) 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 31 ways as a sum of consecutive naturals, for example, 1107521 + ... + 1108121.

It is an arithmetic number, because the mean of its divisors is an integer number (25081728).

Almost surely, 2^665800421 is an apocalyptic number.

665800421 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

665800421 is a deficient number, since it is larger than the sum of its proper divisors (136814875).

665800421 is a wasteful number, since it uses less digits than its factorization.

665800421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 813.

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 665800421 is about 25803.1087468158. The cubic root of 665800421 is about 873.2019330922.

Adding to 665800421 its reverse (124008566), we get a palindrome (789808987).

The spelling of 665800421 in words is "six hundred sixty-five million, eight hundred thousand, four hundred twenty-one".