666665421 has 16 divisors (see below), whose sum is σ = 963065664. Its totient is φ = 408570624.

The previous prime is 666665399. The next prime is 666665449. The reversal of 666665421 is 124566666.

It is a happy number.

It is not a de Polignac number, because 666665421 - 2⁹ = 666664909 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666665621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 149806 + ... + 154191.

It is an arithmetic number, because the mean of its divisors is an integer number (60191604).

Almost surely, 2^666665421 is an apocalyptic number.

It is an amenable number.

666665421 is a deficient number, since it is larger than the sum of its proper divisors (296400243).

666665421 is a wasteful number, since it uses less digits than its factorization.

666665421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304060.

The product of its digits is 311040, while the sum is 42.

The square root of 666665421 is about 25819.8648524736. The cubic root of 666665421 is about 873.5799206409.

The spelling of 666665421 in words is "six hundred sixty-six million, six hundred sixty-five thousand, four hundred twenty-one".