666155421 has 20 divisors (see below), whose sum is σ = 1053659772. Its totient is φ = 417979008.

The previous prime is 666155407. The next prime is 666155443. The reversal of 666155421 is 124551666.

It can be written as a sum of positive squares in 2 ways, for example, as 419225625 + 246929796 = 20475^2 + 15714^2 .

It is not a de Polignac number, because 666155421 - 2²⁵ = 632600989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666155401) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 240510 + ... + 243263.

Almost surely, 2^666155421 is an apocalyptic number.

It is an amenable number.

666155421 is a deficient number, since it is larger than the sum of its proper divisors (387504351).

666155421 is a wasteful number, since it uses less digits than its factorization.

666155421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 483802 (or 483793 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 666155421 is about 25809.9868461803. The cubic root of 666155421 is about 873.3571005160.

The spelling of 666155421 in words is "six hundred sixty-six million, one hundred fifty-five thousand, four hundred twenty-one".